I stretched my sxr700 out to 144". I used track usa rail extensions. Awesome fit and stronger than the rest of the rail. For tunnel extension, I had an old junked out Indy chassis(I think it was an Indy 650) that I cut the back 12 - 14 inches of the tunnel off, slid it into the Yammi tunnel and riveted it on. It fit like it was made for it. I used a 2" paddle, so I had to drop to an eight tooth driver. I found out the hard way that having the track tight enough not to ratchet means that the slides will only last 100 miles. To remedy that, I put Wahl Bros. extrovert drivers on.
I had it out in the Snowies last season and easily out climbed a piped 141" mountain max. I was pleasantly surprised with how well it ran out.
