Ouch! A 6.5? My observation of K&B 5.8 and 6.5's is that they are speed engines, not "R/C", and they vibrate in the mid-range. If losing a carb in flight is cool then they be s-o-o-o cool! A K&B 40 or ST G21/40 might make you a lot happier but what do I know? In any case, if you use a pre-1978 cross-flow engine, you'll get an extra 20 bonus points and you'll have a not-so-nose-heavy plane. You'll also get 20 points for the plane.
Lee, how are you going to cut the slot in the case? Do you have a jig ? Ron