I wouldn't worry much about the SU's, the beauty of the design is it self adjusts to altitude. My TR lives at 3300', it regularly (well, in the summer) goes to the cabin at 6200' over the Beartooth pass at 11,900' and into Yellowstone park mostly around 7000'. It has been to Victoria BC at sea level and toured the Michigan UP. Never a problem. Had some DCOE's on it for awhile, made my life miserable.