Hi Pete,
I think you are getting me confused with somebody else. Everything that I have done so far with these 31's has been to improve reliability. I currently have 3 31's that are flyable. 2 of them have been in the air. The 3rd one hasn't flown yet but will be flown soon.
The 2 ring or single ring issue, as far as I can tell doesn't seem to matter. 1 of my motors is a single and the other has 2 rings. At the field one day I swapped motors and got nearly the same preformance. I used the same prop, 18X10 Dynathrust.
The 3rd motor, hasn't been flown yet. It has a single ring and it was a long shaft. I cut the crankshaft down, drilled centers in it and single point threaded a 5/16 -24 thread on it. I ran it thursday before the heatwave started and it started right up. On this long shaft 31 the keyway was not on center. It was off maybe 5 degrees. The motor seemed to idle slower and smoother. The top end didn't seem to be as high. I'm running all these motors on the stock magneto.
With the motor mount and reed valve issue. All my effort has been to get away from the molded reed valve mount and then to incorporate a better engine mount that spreads the torque out more evenly on the firewall. I use 3/8" 7 ply for my firewalls.
Larry