i posted to that thread when i got the simo up and running.
it rips in the midrange, and has me up to about 35 on a bone-stock C cylinder. the lowend is really crappy though, to the point that i have to pedal it off the line when i'm starting on a hill, but once i'm up to about 10 mph, it will go up walls. The stock cylinder porting on those is such a bitch though, without porting its impossible to break 35. I'm also runnign a 16:16 dellorto, but there is really no point in going over 14mm for that setup.
I'm putting on an athena 80cc reedvalve this weekend... should be interesting.
The simo pipe is really sized for a kit, not stock. It should really rip with a 70 or 80cc kit. I should have the mounting brackets available for sale in a week or so here.