I weighed my GT today with the 12x10 coil. I had removed the detector stand I built as seen in the above photos, and instead used rubber feet on the bottom of the control box. The box is sloped down so that the rear portion of the control box is the first to touch the ground, so I installed two rubber feet at each corner towards the back (face plate area). If you notice there is a line where the separate face plate and bottom portion of the box come together. For that reason I installed the two rubber feet right along that line but on the control box bottom side of things. Reason being is that if you were to mount those two feet on the face plate portion I think that might loosen that up over time as stress is taken on and off the feet when set down.
The custom light weight GT, running a lipo, and using the 12x10 coil without coil cover and instead having spray on bed liner on it's bottom to protect it weighs in at I think 4 pounds 3.7 ounces. The exact number is right around there but escapes me at the moment. No matter, as I have to weigh the coil separately with and without coil cover as well to update the Coil Comparison & Weight Chart I posted in another thread that I compiled. I can say that the stock 10" coil without coil cover using spray on bed liner weighs exactly .3 (point 3) ounces more than before the spray on liner was put on. Compared to I think (see chart) 2.5oz for the coil cover you can see that's quite a weight savings. From memory (again, see chart) the 15x12 without coil cover is lighter than the stock 10" coil with cover still on by about .6 (pound 6) ounces. I'm anxious to get this 12x10 off the shaft and weight it with and without cover, because by feel I think it's much lighter than the stock 10" coil, at least with the cover still on the stock coil compared to the 12x10 without it. As the 15x12 shows that should probably be very true, and I'd expect much more in the way of weight savings. I'll re-weigh/confirm all these numbers and post them within the next day or so.
By the way, for those of you who have been nagging me in PMs about the $20 price of the Whites Tall Man lower rod...First, that's pretty cheap considering what you are getting being much lighter than the Minelab lower shaft and all, not to mention cheaper. Anyway, I headed out to my local Hobby Town today and sure enough they had a Tall Man lower coil rod for $10 sitting on the shelf. Needless to say I snagged that right up for my S-5 coil to mount to, making coil changes a lot easier between that and the 12x10 on my land rig. I mainly hate having to remove the coil nut/bolt and wiggle that out, then manage the new coil on with the four rubber washers (required since Whites rod mounts aren't as wide as Minelabs) without them shifting on me and closing up the hole. Note to mention the fact that I won't have to re-do the Velcro for the cable going up the shaft. Just will have to wrap the cable around the upper shaft behind the grip like I like to do, plug it into the meter, and away we go. The 10" coil stays on my water rig (the stock GT shaft and arm cup, though with a end bar as well and a more comfortable rubber grip to replace the stock one), so I don't need to worry about that.
If you go the route of one of these Whites tall man rods make darn sure it's the lower coil rod you order and not the middle rod. You can then either order 4 of the Whites rubber washers or head up to your local home improvement store and pick up a package of those rubber faucet repair washers. They have various sizes, so I'd bring your rod up there to see what fits inside the washer hole on the Whites rod. You'll have to drill out the center hole on the washer more than likely. Like I said before to, if you are going to order that lower rod from Whites then for another $10 you'll get an arm cup and strap that is MUCH lighter than the stock Sovereign one. Those two things alone will save you a good bit of weight.
The Whites rod is roughly twice as long as the stock Minelab one. You have two options here. Either just stick the Whites rod all the way up inside the upper stock shaft and then drill your snap pin adjustment holes where they need to be, or you can cut the Whites rod down to proper length, but you'll still need to drill the two snap pin holes out on the Whites shaft this way too. Either way, even without being cut down it's still lighter than the Minelab fiberglass shaft since the Whites is carbon fiber. An even better solution would be to cut the upper Minelab shaft down in length to save all that extra weight, since the Whites rod is much longer and carbon fiber is lighter than aluminum. Then instead of drilling new snap pin holes on the Whites shaft, you just drill them out on the Minelab shaft to match the length of the Whites. If you don't want to modify the stock shaft for re-sale value then find yourself a lighter grade aluminum than the stock upper shaft and then cut that down to length to match the longer Whites rod. That's what I did because it's the lightest solution to max out total weight savings.
I used the inner extension pole from an adjustable window cleaning pole made by Unger. They sell these at most home improvement stores. Unger has a green hand lock. Ettore (spelling?) uses a blue hand lock for pole adjustment but I think the diameter of the inner pole on those is the same too, but it might be a bit heavier. Not sure. I just remember back when I was in the window cleaning trade that the Ettore poles of the same height were heavier than the Ungers, so they might be higher gauge aluminum. As an added bonus, these window cleaning poles have a two headed snap pin in them like detectors use, so they make a good spare to have around in terms of that. In my view you don't need cam locks when building your own rig like this. The trick is to drill out both snap pin holes on the shaft. The stock Minelab shaft only has one hole drilled yet it contains a two-headed snap pin for shaft adjustment. Even on the stock shaft I drilled the other one out, because that makes things MUCH more snug then some silly cam lock, which from experience on any machine strips pretty quick anyway. Drill out your two snap pin holes on the stock shaft even if you are only staying stock. It'll stiffen it right up. And for sure drill two snap pin holes on any custom shaft you make. Makes no sense that Minelab would put a two headed snap pin inside the shaft and then be too lazy to drill both holes out on both sides of the shaft. Makes all the difference.
My GT is so light now that about the only thing I could possibly do to create more weight savings would be to shorten the length of the coil and meter cables. I think that would roughly save 4 to 5 ounces. The only other thing would be to replace my lighter upper aluminum shaft with a carbon fiber one. I'm looking into a cheap local source for one of those in that diameter. I know where I can get them dirt cheap on the net (about 1/5th the price of conventional carbon fiber producers), but I hate to mail away for something like that when it weighs nothing and I don't feel like paying added cost for shipping. I know locally where to get my hands on smaller carbon fiber tubes but not something of that diameter. I would guess that if I replaced this upper shaft that might save me another 2 or 3 ounces if my new upper shaft even weighs that much. Can't remember. Figure with shorter coil/meter cables another 4 or 5 ounces for that. I could probably get this machine down to around 3 pounds 11 ounces or so at the absolute limit in weight savings with the 12x10 coil or stock one. That's pretty darn outstanding, as I already feel pretty proud of how light I've made this thing thus far. Not to mention more user friendly with the remote PP and meter on top of the grip. As comfortable and light as any other machine I've owned, barring a Tesoro of course.
No joke, I bet it is, unless somebody used the old trick we used to do with RC circuit boards and shave down the edges of the Sovereign control board as much as humanly possible. 
