You are not going to stretch that belt in the least, I promise. They'll burn up and break. But you ain't gonna stretch it. So you can roll it on off there, and not worry. But if you can spread the secondary clutch sheaves, it'll make it much easier to remove and install. It is possible to force the secondary open, by pushing the belt down into the sheaves. If you have a belt laying around that you're not gonna use anymore, I've seen some folks cut a small section and use that to push in between the sheaves, when removing old belt, to hold them apart while you can more easily get new belt on there. Most effortless way would be to get yourself a clutch puller for the primary.
It's a shame Polaris doesn't put roller secondaries on all their machines, makes it sooo much easier.