RE: .049 VA split case
There was a number scratched on the top of the piston and I believe this had to do with the fit with the cylinder. The rumor at the time was you wanted a lower number. I think it went from 1-4. I had 2's and 3's.
I actually have one that was polished and ported from George Aldrich himself. He really like the engine. I still have it. Problem is it got mixed up with the rest of my VA's. I think the rarity is just the fact they are not made anymore. The MK II really was a screamer. Getting close to the Cyclone. I could get mine up to 25,000-27,000 with the 4" props we used in combat for that moment in time.