There's some bs floating around about moment of inertia if the engine is out too far. If you drill the front holes about 1/4" from front of mount, it'll be fine. I still had to use a heavy Higley hub inside spinner to get a 4 1/2" cg. I had a TT 46 to go in it, but I didn't want to cut so much of the side cheek for the exhaust, which lead me to the TT 54 4c.
For starts, don't go past the 4 1/2" cg. Too many expert pilots are suggesting rearward cg to intermediate pilots. Not many average pilots can fly helo-planes.