Hi Steve:
Although I am new to the 70 I did get the 10.5 7.5 coil with mine and have used the heck out of it the last week and a half. Everyone in the club I belong to here on the Eastern Shore that owns a 70 really urged me to get it, not only for beach use but for coin as well. Last Saturday the group went to a CW site in Accomac Virginia and those with 70's and the DD did better tan anyone else.
I had trouble with mine on the beach day before yesterday but since found out with help from two forum users that I had the sense set too high. The best way I can describe it is that it cuts through the ground like a knife.
I made myself a test garden a week before it arrived. With clad and copper at 12"'s and I can find exactly where they are.. not even using the pinpoint feature. I can actually find exactly where I have buried the items by not only using a X pattern, but by also using a cross. When I made my garden I put two golf tees pushed flush with the ground on each side of the coins. That is how I can tell I am getting an exact reading. Again, I had some problems in the sand with it, which you say you are not going to do.....but those problems were of MY own doing and I just have to get better at it.
As one of the fellows told me...practice, practice, practice. Don't get your blood pressure up. It does have a learning curve, but the fellows tell me that when you get through that curve you are going to find things others will miss.
Also, when you use the 10.5 watch the threshold. If you have it up too high you might miss a faint signal that could be a great find.
Good Luck in your hunting.
Elf (Albert)