Heres a couple others.

I used a 1/8th in ply plate in front of the removable hatch on the plans. Shortened it 1/8th inch and put the plate in on the back side of the bulkhead as I remember. You could also re-build the bulkhead to include it and not shorten the hatch. Then I made the hatch over the tank out of solid balsa instead of trying to build it up. You could do that and hollow it, but I didn't. Just used a solid piece and sanded it to shape. Lip in the front goes under the front sheeting, and a screw in the back. You could also use smaller plates front and back and use 4 screws to hold it on instead of the lip.

Hope that helps.