Did you try to adjust the shift rod trunion ? Not sure about the 926,XXX models, but on the multi-speed Compacts you can adjust the trunion 4 turns or so to slow the unit before wheel torque becomes a problem.
If you mean moving the friction wheel closer to the center of the drive plate I did do this and it helped a bit
but not enough for my taste. The side effect was that 2nd reverse can no longer be engaged , something
is stopping the friction disk from moving over enough (though 1st reverse is now probably close to what was
2nd reverse). I haven't had a chance to open the machine up and see what it is. In first forward there must
now be quite a bit of sideways movement to the contact patch on the rubber, which can't be much good for it.
I'd like a big reduction in speed. I could live with losing the top two or three forward speeds if it would buy
me a good strong creep speed. I'm regularly facing one to three feet of snow since my cottage is on a mountain
and I don't get to go there more than every other week. I'll take a look a the drive pulley and do some math.
Even in town the only time I use fifth or sixth gear is to cross the street.
Paul