I have now had several good weekends with the PAW 19 using the MAS 9.5x6 and Aerodyne fuel. Looking back it seems that the vibration problem was a combination of undercompressed and very rich mixture. It may have been just on the verge of hydro lock with the extra liquid giving the needed compression to keep it running. Anyway all has been fine and I now want to try to low the lap time for 4.8 sec (60 ft lines) to 5.0 sec. I will try an cut down a MAS 10x4 to 9.75 and repitch (heat gun) to 4.5 to start. The engine is turning at 10.4K rpm on the 9.5x6 so I think I could load it to reduce the rpm to 10K even and still have a smooth run.