MORE? Is it bottoming out? How are your springs set? How about the spring on the shock? I have that exact sled and have NEVER bottomed it out. You might want to look into doing some adjustments first. Also check the condition of the springs and the spring perches. How many miles are on this sled?
If your trying to supercross it, then omit the above questions.
First off, to properly do something of this nature it can get expensive ( as in buying a new skid). The skid in there now is designed for the travel it has. You would be better off selling the sled and taking that money and the money you would have to put into it and buying an edge chassis sled. Second, If you jack up the back you would have to jack up the front also or have far too much ski pressure due to the hotrod stance. All the weight would be on the front. You should be able to adjust that sled to make it ride pretty damn good without jacking it up. Maybe just start with some shock rebuilds (or replacement if not rebuildable).