As for engine mount..  I have an angle valve engine in a short mount.  Correct me if I am wrong, but if the engine weighs more, I don't think you want it further from the C.G.  I have the small tail, maybe the big tail would react differently.

Getting the cowling to fit, and look good, sucks..  I'm still looking for a good solution.

I also think angle valve engines cool better.  Takes less air to get the same CHT's.  I have itty bitty cooling intakes and I have never seen anything over 350 CHT.  My new cowling will have much less cooling air exit area.  Maybe balance things out and bring up the CHT some.

Tom
www.N54SG.com