i run a MVVS .45 with Pretner carb ie the butterfly type , excellent engine with great transition. This is on a bipe. Use homebrew fuel with 2.5% nitro. OS # 8 plugs. Props is 10*6 upto 11*6 .
i also have a .46fx . but is only happy with 10*6 prop on same fuel and plug.
I am using the quiet silencer but a minipipe the MVVS 45 will put up another ~1000 rpms.

in the long run the Mvvs is a winner . imo.