U Can Do 3D
Bruce,
Just use the stock tank. Its 14 oz and should easily last 15 minutes (or more) depending on your throttle usage. 3 of us in our club are using the stock tank with the YS91 without problem. I haven't heard of anybody on RCUniverse bursting the stock tank with YS engines. I have yet to run the tank dry. You don't fly these at full throttle much.
Chris