I have an atemoya from seeds I've started. I have a sugar apple from seeds I've started.
I grew tired of the atemoya never setting fruits so I moved the sugar apple (in a 3 gal pot) next to the atemoya growing in the ground.
The atemoya had a lot more frost damage. That dead area grew; making the tree smaller by the week. After cutting 4 ft from the height; it began to flower.
This past season I picked 4 sugar apples and no atemoyas.
I've been successful hand pollinating atemoya's flowers with a piece of straw.
Looks like this coming spring, I'll be crossing the 2 trees by hand even tho they're 1 ft apart.
I don't suppose you'll get ANY frost in the Keys so I wouldn't know what you'd have to worry about. If you think it might get too cold some odd nights you could always run an extension cord with a 60 watt bulb & hang it near the fruit -- that will keep it warm enough.