Got a buddy that's doing the swap right now. He is using the powderfreaks 6 tooth 3.5 pitch extrovert drivers in place of the factory 7 tooth 3.0 pitch factory drivers. These drivers should be the same size (21" circumference) He got the track installed but it is fiddle string tight and the rear axle is as far forward as possible so no way to loosen it off. The back end of the rails are only about 3/16" from having the track clips catch them as the track goes around the rear axle wheels. Has anyone else done this swap successfully? I'm thinking the actual length of the 155 x 3" track is 156" and the actual length of the 155 x 2.75" track is 154 ". Why else would this track be so tight?