i think the losi mount is junk but for a different reason. i like to go fast and i couldn't gear it as high i wanted to so i used the rcm mount. that thing ROCKS! I do like the losi battery box and the servo/reciever box and center diff cover so i buy them seperately at impaktrc.
i do have a couple of questions for you if you don't mind though...
1. did you put the center diff cover on and screw it down before you sanded the gear?
http://www.impaktrc.com/product_info...oducts_id=3196
(the oval looking thing that goes over the center diff.)
the reason i ask is if it's not screwed down evenly or at all yet, the mount and the mount on the other side can sometimes be mis-aligned and cause the binding. it's happend to me before i put it on.
2. you said you've re-built your roller many times, so this one might sound dumb, but sometimes i forget about it too....did you tighten the diff screws that hold on the gear in a star pattern like it says in the manual? i've done it in the wrong order before and it had rubbed against the mount too. after i re-did it the correct way, it was fine.