Jayco, from my limited experience, some of the Geneva rootstock may do well for you. Last year about this time I planted 18 varieties in my Georgia clay with no amendments on G-11 and G-16 rootstock. The trees I got from Cummins were in the 3 to 4 foot range at planting and grew like wildfire the 1st year. Almost all of them are now 7 to 8 foot and pretty well branched. The 2 varieties I have on M-7 do not seem to like the clay as well and are growing at a slower pace. Chris.

Thanks, Chris. Sounds like M 7 wouldn't do for me then.
Maybe someone who's grown a tree on G 30 will come along.

Jayco,

In my heavy soil I have trees on both M7 and G30. Both seem fine, but the G30 trees have a faster growth rate, and are bearing earlier. Two notes about G30: they seem a magnet for woolly aphids when very small, but to no ill effect and it's not a problem later. And if you plan to graft G30, it's a very brittle rootstock, and is best budded in late summer rather than grafted.

Thanks, Marc, I would be purchasing a whip from Cummins or Adams County, so no grafting myself.