I used the stock tank. Have not run it dry yet, but estimate 10-12 minute flight times tops, safely. (it does guzzle - about 1.5-2 oz per minute). The good thing is if you ever deadstick the thing will float down like a trainer and land easily without power. It really helps to get the low end tuned right. that will maximize your mileage.

make sure you do not mount the elevator, rudder and ailerons to tight to the trailing edges in order to maximize throw. I need to remount my elevator one of these days. the recommended throws are very conservative. I am not a "real" 3D flyer yet, but it seems to me the elevator and rudder have conservative size. I think you will notice that this plane has a little longer moment arm in the fuselage that does seem to amply what looks like insufficent rudder and elevator travel somewhat. Mine US will make very tight loops with no tendency to snap out. I have not got around to trying knifeedge yet, but all kinds of snaps and tumbles, spins, etc are really fun. with ailerons and flaps linked, this thing rolls in a blink. I have just started to mess around with the crow, but it is fun as hell to dive straight at the ground and pull out at the last minute without worrying about snapping into the ground. I'm going to be trying my first vertical dive landings this weekend. After flying Cap's, it is taking awhile to get used to the airbraking qualities of Crow.