i ran a 136 renegade for the past 3 years with limit straps loose and springs set to loosest setting. mine did not trench. this year i will be running and 153 and will start off with the same settings and see how i doo.
rear springs are on hardest, you want just enough to squat the back end but not to bottom out, and the front about mid setting and with sled sitting flat want some slack in the limit strap. you can also set one or two 2x4 under your skies and set it so your track is flat with the skies sitting up.
I'm in the same boat as you. I'm new to sport last year have a 01 700 151 and an 03 800 144. 151 trenched bad last year 800 is new to me this year but people have said to let the straps out all the way so that's what I'm trying now. As for susp. I'm 6'3 280 so I have everything set stiff.
You want to set up your front skid shock softer so it will compress/flatten out attack angle and climb up on snow better,
Use judicious amounts of throttle depending on snow cond. Blipping throttle in deep snow to get on top, I wanted more clearance on my 02 HMX with the wider boards so I got custom drop brackets, dropped skid out of tunnel 5.5", dropped front arm mount down to within an inch of bottom of tunnel, this was all to run the 156x16x2.5 Camo Xtreme track with 3" pitch extros and 19/45 gears. Drop depends on how much clearance you would like, add a deeper lug track and the more tunnel clearance will hep you. Have a lot of pic's of this setup posted here over the last few years. My 02 ZX chassis DOES NOT SUCK in the traction and clearance department with this setup. Track speed is not great, traction and flotation IS!!!