How the COX 010 TeeDee tank backplate seals

At least once I accidentally ruined the tank backplate on one of my 010 TeeDee-s by overtightening the central screw..if forced too much, either the thread inside the tank will be stripped, or the backplate center around the screw cracks.




Playing with my new 010-s acquired recently brought my attention to the backplate which in fact is not flush with the rim of tank body. It means that even if the central screw is not tightened excessively - just enough but not too much - once the engine is pressed by the 2 mounting screws to the plane bulkhead, the tank backplate will contact the bulkhead first, and the paper gasket between the tank and backplate is pressed to seal well when the mounting screws are tightened..so tighten the central screw lightly, the mounting screws will do the rest of the job for a good seal. (It is not meant to recommend the overtightening of 2 mounting crews either, because that may damage the tank as a whole, or, loosen up the central screw where fuel leakage around the screw head may start)





So those who have ruined a 010 backplate before may consider this...I wonder if it was an intentional design feature implemented by COX, or, just accidental?