Gera,
I am constantly switching engines & drivetrains & engine position always searching for the best way to hook things up. Recently just for the heck of it, I removed my 35cc Subaru Robin engine & installed my 2nd Cag w/ RT carb onto the BMP kit & couldn't believe how great it rode & felt. I never ride in the rain, so that wont be an issue going to friction. I also like running fat tires & DH tubes which I cant do on the v-belt drive wheel due to space constraints. I have been using my MB's lately on fair weather days instead of my car & doing anywhere between 50-100 miles/day. If the friction driven tires hold up well enough, I'll be good to go. I did a bunch of gearing ratio calculations & the 1.5" roller will get me the same kind of speeds per rpm as my v-belt setup.
-Lowracer-