best thing to do with that sled and skid is to relocate the skid back a bit and compensate for future track length with some shorter rail extensions.
your dealing with a setup that wasnt intended for deep snow. the whole theory behind the srx was flat ground and wide open runs. however, with attention to detail and some major changes, you can almost make an off trail monster with this sled.
by relocating the skid, you can reduce the approach angle on the track giving the nose heavy sled you just bought a better chance of climbing up on top. from these measures, your track length can be suited to your needs, anywhere from 136-???.
i have spent the last 14 years trying to make mtn sled from my srx. its almost there. 2.5 "lug, 155 " 2.86 pitch camo extreme, works well, countless hours , not to mention $$$. learned alot of tricks along the way.