FWIW, I've got an 03 Summit 700, 144" track.
I did what was described above last year - front spring full soft/minimal preload, rears firm, limiters on the last hole (loosest), then adjusted knob until there was a touch of tension on the limiters.
It was...ok. It trenched a lot, but I figured that was a lot more to do with me than the setup, so I left it alone.
This summer, I thought about it more and decided to try two changes.
1 - Simmons Gen2 skis
2 - more spring preload.
I'm ~300# on the sled, and was bottoming the front shock out on whoops. I figured more preload would help there, and as long as things did not get _worse_, I'd be happier not bottoming out all the time (it was bad).
I've only ridden 3 days so far, and not one was in truly deep snow (duh), but the difference is night and day - I've sought out deep snow/soft snow, found some fairly soft drifts (posthole to mid-thigh) already, and it seems very, very good so far. I'm not sure how much of it is the skis & how much is the added preload in the front spring, but either way - the sled is nowhere near as trenchy as it was; it climbs out much easier now.
I rode one day with a guy I normally ride with - he and I were about the same last year in terms of skill. The day we rode together, he got stuck countless times (ok, six, five of which in a 200' stretch - stuck, dig, pull, get ready....stuck again. Repeat). I got stuck zero times, including riding "his" sled around to see if my sled just got THAT much better.
It IS better, but not that much.
So, yeah - the above suggestions seem "right," but as a bigger guy, you might consider adding a couple of notches of preload (my sled has the rotating/stair-steppy preload thing, I added 2 clicks) to the front spring. That's the real/bigger change on mine - I also loosened the limiters some. My setup is basically what was posted above + preload.
I like it. I think that the added weight was starting the skid off in the "wrong" spot, and the additional preload puts it back to where it would be with the above setup - which probably works great for 180-220# people.
Iain