Abu
If you go by what is on that thread the only differences between the A and B are a back plate and cam housing. Nothing that would alter the operating characteristics. If the "B" runs differently than the "A" there are other changes that just aren't obvious ie compression change cam profile/lift or crankshaft dynamic balance. The thread wasnt info from a company source but rather hobbiests opinions. Since it seems you are finding improvement on your own just by continuing to work with it then you should do just that till it's well and truly broken in and adjusted. then mount it on the Cub ARF and fly it. Then later if you so choose go ahead and do whats necessary to mount it to the Snipe (if you want) or save it for a future project. It's not that much bigger than the 72 and though I dont know the horsepower ratings the gain is likely to be unworth the hassle. Your wing loading is very light and though the power loading is as much as I'd want to work with I still think with some altitude you will find you can slow the airplane down and learn to enjoy flying it. It's always a bit of a strain getting comfortable with a model you have spent so much time and maybe money on when comitting aviation but once you do begin to relax with it you'll have a lot more fun.
Doc