I used a 4 oz. Sullivan tank, can't remember if I used the round or cylindrical shape. The cylindrical is slightly smaller in diameter, and longer. I just had to cut out a bit of the instrument panel to allow the tank to protrude into the cabin. I mounted an HS-55 for the throttle to the right side of the fuse just behind the tank and wedged a piece of foam in between the back of the tank and the servo mount to keep it from sliding back. Worked out great. If ya want, I can zap off a pic and post it.

Wh00ps!