gearing sled down

Geared my old 98 PS to 16/42, worked great, top speed was only 70mph though.

Factory setup for your sled over 5K elevation was 19/40. Years ago I had an EXT 530 with a 136 slick track under it. When I swapped to a much deeper lug, I geared it down from a 20/40 to a 18/43. I thought I would loose about 10% on the top end. It turned out that the clutches weren't shifting all the way out with the original gears. I lost no top speed and it was a much better machine off the trails. I would bet that the 18/42 or 18/43 (which ever works for chain length) in your sled would really wake it up without slowing you down too far.