RE: Going CL with tis R/C model
The bellcrank mount really needs to connect with at least one substantial structure. Fuselage walls aren't enough. Connecting to a bulkhead is a good idea.
The CG works for flight, any kind, even tethered flight. It's a pitch stability deal and how the surfaces are driven doesn't change that and the leadouts don't influence pitch stability.
If your old engine runs reliably, you really don't need more. And you certainly don't want more weight.