Along with the longer belt, you could probably go with a softer start on the primary spring as well which would cause the engagement to happen earlier and give you smoother/easier take offs.
I don't know what stock is exactly, I don't know what part number that is (0151-1007). Can't cross reference it... Probably a CVTech R&D part number.
If I were you I'd probably try a Yellow/Green from Bombardier (part # 414742100) which has a 100-260 force to it. That 100 pound start force on this spring won't retain a lot of inertia and will engage at a very low RPM. Probably a good thing for guys who are still in their learning curve or who are just looking for a less agressive ride. A 600 at Sea Level is more than a lot of guys can handle anyways...
Once you get use to it, then you could go back to a more agressive setup. BTW, a spring is pretty cheap, like 30$ at your local Doo dealer... but you need a clutch puller stud, clutch holding key and a spring compressor or you can have somebody that has the tools to do it.