Hey I saw in a Dirtwheels or Quad mag they make a aftermarket CVT belt and Gear to handle tires like these. My buddy Doogie has a 700 Grizzly he did the belt and gear on and it made a huge difference for the bottom end and low end torque. He can actually get his up on the back wheels now that he has the belt and gear.
I cannot remember where he got it from but I will ask, if you are interested.
i know nothing about these utility quads, but i do know about cvts and those tires will be slipping that belt. you may want a higher quality belt and you can tune the clutches with springs and such, i even tune the cvt on my golf cart as far as different pucks.
dayco makes some nice belts, and have a good warrenty.