I built one from 3/16" fom-cor board with 10-cells and an endoplasma, 4.6 gearing and 12X8 "E" prop. Weight was 46 ounces and it would easily pull from hover untill the very end of the charge (average 8 to 9 minutes due to the extremely low throttle during most of the flight, hover was about 35%~40% throttle). Too many flat spins into the ground and it was just too beat up. Must build another one though,.. lots of fun . the smallest i've seen was posted in a thread on ezone, made of 3mm depron, i think it was 5" square with a KP00 motor and magnetic actuators. Just under an ounce ready to fly. They had some video posted of it flying in a gym.

I was wrong, it's 8" square, 23 grams,..link is here:
http://www.rcgroups.com/forums/showt...&highlight=PBF