When I did mine, I just sent my case to mpi and they sent me a modified case. However I purchased the tunnel directly from them. They are good guys though, very helpful and I am sure for a small charge, they would set you up. First though, I would see if youcan get a case with the tunnel, your Mountain Max and that SX should use the same case.
As far as the drop and roll. On your MM the jack shaft runs over the top of the tunnel and the chain case drops pretty much strait down to the drive shaft. On the MPI tunnel, The jack shaft is lowered and actuall runs through the tunnel just a little bit above where your drive shaft ran through the factory tunnel. To accomidate this the bottom of the chain case is rolled toward the rear of the sled. The end result is that your drive shaft is aroud 2in. lower and 3 in. farther back. The MPI tunnel has the rear skid moved back accordingly and what you get is a much shallower angle of attack on the front of your track. This helps keep the track form trenching and it really lets it just climb up onto the top of the snow.
On another note, I just remembered that the MPI tunnel gives you room for pretty much any track/driver combination and I took the opportunity to go to 9 tooth extroverts on my Viper. Certainly not nessecary, but a suggestion.
Hope this helps.
