Mine has the Norvel .074, because I couldn't see a good way to mount a .15. My Pica Messerschmitt has a .15, and it's a rocket, and the inverted .15 fits well.

If you cut off everything forward of the firewall, you'll probably have room to mount your .46. You're right to ask about balance, there will be some tail weight necessary to balance it.

Good luck,
Dave Olson