[EricH]

If you were doing a fixed-wing aircraft, I'd come right out and call you insane. Seeing as you're doing a rotary-wing bird... You're still insane, mainly for trying anything rotary-wing (they don't fly, the ground just repels them).

Be that as it may, the 15+lb of the FRC battery is not your friend. You're talking about designing a 20+lb quadcopter, and that's just the CIMs and battery. That's not easy! (I spent several years in SAE Aero Design, and most planes couldn't carry much more than about 20 lb, and that strained them.)

Now, I ran the same sim with slightly different numbers--including a much more realistic frame weight estimate. (<2 lb? When you're carrying the battery? Seriously? I bumped that up to about 6 and a quarter lb.) I got a 9 minute flight time, 25 minute hover, on 18-4.7 props.

If someone REALLY wanted, I might try to mock one up in my R/C flight simulator, battery and all (I can think of a few ways to go with that) and try to fly it (my rotary-wing flying skills almost never end in a great landing, though on simulator they're all good landings, by the standard pilot definitions).