Holeshot inc has a good defrost bag you might want to checkout. Dash Bag // Polaris Rush/RMK | Holeshot // Performance Driven Parts
Depending on how much you like to use trees for traction I would put a different bumper on to protect the sled a bit more. Polaris has this bumper Polaris Snowmobiles CA similar to the Dan Adams which I went with.
Change out your primary spring for an SLP blue/pink one. Will give you an extra 100-150 RPM at elevation!! And they dont break like the stovk ones do!
X2 the idler wheels if you plan on doing some flatlander riding or like spring riding these things will heat up fast with no slider lubracationSpare belt and plugs if you don't have them already. Additional idler wheels if you ride lots of hard trails.