NOT a "will they fit" question

There always that chance. Jumping from 28's to 30's on my clutched and tuned 1000 there was a noticeable power loss.
You're adding rotating mass and effectively gearing the machine up. Which may be hard on belts with your 800. I run maxxis carnivores and they're one of the lightest 30's. And come in at 33lbs a piece. Many are 40+ lbs. I'll be going back to 28's when these wear out.

Whichever size you pick. Pay attention to tire weight before dropping the cash.

Good answer. Thanks

I got some 30” Carnivores on System 3 headlocks coming. Not sure of the combined weight yet but I’m sure I’ll have to clutch for them. To get the clutches to perform approximately like factory can I just put a stiffer spring in the primary and if so which one? I used to spend a lot of time adjusting snow machine clutches for hill climbing but that was a LONG time ago. Can’t remember most of what I learned.

I'd did my fair amount of sled clutching also. There's a different learning curve with these low hp rpm heavy machines.

Swapping to a stiffer primary will only net burnt belts.

I'd recommend getting a kit from rvs performance for the appropriate tire size. Which will include primary, secondary springs and a weight change.