That is a 12 oz. tank. The rear of the tank is flush with the former at the front of the "wing bay". The front of the tank is 1 1/4" from the firewall.

The hatch is nothing more than a piece of balsa stock shaped to match the curvature of the fore deck. 1/4" square stock is added to the bottom to position the hatch left/right and front/back. I added some stock to the sides and back of the fuse to provide additional support. Not sure it it's structurally needed or not.

Btw - Ihave a YS110 on the plane and 12 oz is fine for a 12 - 15 min flight. Of course, very little (repeat - very very little)of the time is at anything above 1/3 throttle. Yea, overpowered by a "bit".

HTH