I still have the stock heavy Yokohama 141 on my sled, soon to be replaced hopefully with a used Camoplast 141, 144 or maybe 151 depending on what I can find. A 144 Camo is 15lbs lighter than my 141, plus it has a much more open lug pattern for better trackspeed. The Ekholm tunnel drops the drive axle 2" and rolls it back 4" so the shaft goes through the front of the tunnel. It's the hot ticket to making the MM work in deep snow, even with 9 tooth external drivers the approach angle is really flat. 10 tooth is even better but the drivers aren't cheap.
I'll have to check out the new Polaris tracks, I didn't know they had something new out. Sled technology moves fast so I stay behind a few years to get cheap used parts off the guys with the big money. Seems 156 and 159 is the tracks to run this year, yikes!!!