If you go higher riding, which is not easy, then you will raise the sleds center-of-gravity. All you would gain is some added tippiness, which is not desirable. The easiest way to get your person higher is to increase the padding in the seat or get an elevated seat.
To get the rear suspension "up" (i.e. lower the rear suspension) you would have to lower it's mounting holes in the tunnel. Doing that and maintaining the track's approach angle takes a bit of calculation and measurement. There is a thread on the site, where one of the users put together a calculation worksheet to assist in this. It was at the top of the RX1 Forum around Oct-Nov 2008. You may want to try a search on "calculation", etc.
But, I would not raise the sled doing this. If i was going to attempt something like this, I would be looking at putting in an after market suspension. The reason is, no matter how low you mount the skid, you are not going to gain travel.