John,
The only SEF coil i have is the 10x12. I recently pulled it off my DFX and installed it on the wife's M6.
Went to an old one room school site that i had been over many times with the DFX. The M6 sniffed out
Six more wheats, and indians, plus a super thin barber dime that i missed with the DFX. I was running
correlate on that machine, and not 15 Khz raw like the M6 is. Also did some sidewalk hunting in town
and found some nice deep stuff with the M6 and the 10x12. I don't think you'll be dissapointed at all
if you should decide to purchase one. Don't know if coil weight is an issue for you, as they are a bit heavier
than the standard concentric coil. They can also be a bit tougher to swing in high grass, and bean, or corn
stubble.. Another small problem is learning to pinpoint with it.. But the learning curve is short on that.
If you are hunting areas with a lot of surface trash, you might want to go with the smaller SEF coil.
If there is an aluminum can on the surface, sometimes the 10x12 will pick it up even if you're a foot
to the side of it. I guarantee you it will pick up deeper stuff that you've already been over with the
standard coil. I was blown away by the items that had been missed previously with my standard coil.
Good luck with whatever you choose. HH Tim