RE: OS Max 55 AX issues
If you were to get a Saito the 72 or 82 would be the standard set up. Your initial problem is the 13x6 which is a high RPM 91 size. I would not rule out the OS 55 yet till you find the right prop. The 12.25x3.75 is the perfect 46-50 size. Hobbytown or Wildcat 18% total oil with a 80/20 castor mix will be good. The MAS 12x5 K blade should be a good choice. A little more speed with some good pull. If you already have plenty of cool power just add some castor to it. I think Brainard has a race track so castor can be bought at local speed shop or Kart shop without having to drive 2 hours. Even drug store might have castor oil.