Well, I just changed my .21 from a 2 shoe into a 3 shoe... You won't be able to use the flywheel from your .21... It will only have two pegs. You can't fit 3 shoes with only 2 pegs. I bought an Ofna lightweight flywheel with 3 pegs for .21/.25/.26 engines.. Mugen has aluminum shoes, but I just wanted to try using the regular fiber shoes, so I bought the HPI shoes which came 2 in a pack and just used one of my originals. I had to do some modifications because the clutchbell would bind with the spur gear. I grinded the brass collet a little which brought the flywheel closer to the engine. Grinded the brass end washer so that it would not seize the clutchbell to the shaft. I'll run it tomorrow to see if the 3 shoe made any improvements. I tried it in the garage, 10pm, and it seemed to hook up a lot better.
