AeroDave,
Are you using a cup mount?
The distance from the back of the cup mount
to the front of the prop flange is 6 5/8"
on my engine.
I think that's close to what they are calling for
from reading the threads...I don't have mine yet.
Going to have to call my not so local hobby shop
to see if they heard anything from GP.
(30 Miles) maybe I should have ordered from Tower
They were offering $40 off if I spent over $500 bucks
I would have done that easy.
I'm not in a real big hurry, I'm trying to finish up a 1/3
scale Laser 200 our group scratch built six of em.

Bob