Cutaway,

Your tank looks like a GRW-type chicken hopper/shallow wedge strapped onto about a 1/4" foam base. Close? Depending on your airspeed/laptime, that might put the 'reference height' of the tank (thinking the direction of loads in flight) pretty far outboard. That could relate to the needling problem with the Stallion, but it does sound like that's legitimately worn down some.

Nice looking bird! Appears to have ample wing area to carry noseweight you might need. Keep the word coming, and Luck!