I moved mine back 2.25 inches to run a 151 without rail extentions and improve the angle of attack at the same time. I ran into problems with the track hitting something though. The more I tightened it the less it happened so I am hoping that it was just hitting all of the rivets poking through the tunnel because the snow was all wiped off and I am sure I saw rubber under there. Local movers come here - site company. I rolled the end of the rear mount up one spline but don't think it is enough to make up for the raised location of the new mounting hole which is already as low as I dare make it with only .25 inches of steel around it. I also had to cut a washer in half and weld the halfs to other washers because the new hole is centered just below the weld where the steel is doubled up. I think I might weld some drop brackets to the bottom of the tunnel to lift the rear of the sled some more so I can loosen up the track again. It is so tight now that any gains I made by improving the ange of attack are most likely eaten up by the added friction. I am going to move the skid back to the original location ind install the rail extentions until I have time to weld up some brackets.