I just bought a 2004 summit x 144". We were riding deep powder today in BC, Kootenays, and the sled seemed really sketchy, breaking trail and following fresh track. It would not hold a line well any place and when following in a new track would dart off the side and submarine. All the riders felt it was the most unstable sled to track. We noticed the front end (slid) was much lower off the snow than either the 700 dragon (163) or the m8 (153 I think) we had along so that may have had an influence. I'm not sure if the newer designs sit higher up or not by trait. In the parking lot both the other longer sleds would turn inside my 144 track by a large margin. my sled just seemed to slid wide, so I am blaming the skis at this point. What do others think from experience? Also would extending the track to a 151 make it a noticeably better mountain sled? Or is 144" enough?