Thanks for the info. I made a "Bottom" for the tank out of EPS foam.
Top and bottom with a balsa brace in the back.
At 4 1/4"" back CG, mine balanced level with a 5-cell Ni-Cad pack right behind the
tank. I used a GP balance machine. What I did was mount everything except the
battery and moved it across the fuse bottom until wings level.
I had a prop and spinner attached so I am surprised you had to mount the battery
back so much in the fuselage.
Hmmm. where did you other guys mount your battery pack?
The TT .91 is kinda heavy but the plane sits level at 4 1/4" back from the TE.