Just cause I love sledding - I will add my .02

As far as your equipment dont overload your sled. It will make you top heavy if you get on a hill or deep powder.

If you are on a 2 seater turn your pack into a back rest or a bigger back rest for your passenger. If no passenger, lay it flat so you can lean against it.

other then that the key to snowmobiling is NOT to get lost stuck or broke down. Most of the time (recommended all of the time) you will be with at least one other snowmobile. Have equip to:

stay warm
find where you are/where you need to be
eat / hydrate
be rescued.

I am not down playing any suggestion put forth, it has been my experience though that you pack enough to walk back to your camp / trailer. If you plan on making distance (100's of miles) have a cell phone / sat phone and an extra battery.

I am jealous, have fun and WEAR A HELMET!