to answer your questions:

1) landing gear holds up fine. I have had no problems when mine is loaded up with the G26, 20 ounce fuel tank, smoke system, three 6 cell battery packs, and 19 ounce smoke tank. I don't know total weight of mine, but I have not had any problems with gear
2)Should be plenty of clearance with a 20 inch prop. I use a 18-6 prop and there is lots of additional clearance yet. I haven't even come close to a prop strike.
3)you could definately fit a 32 ounce or higher tank inside. The interior is cavernous to say the least.