I have the same machine and did is what you are talking about 156 to a 159 on a 2002 800 polaris and what i did was move the entire suspention back 1.5 inchs which is also giving your track a better attack angle works great had it on the sled for 3 seasons now and zero problems.
THE boys are up in revy as we speak. Talked to them yesterday and frisby was groomed friday night, starting at the 2 k mark. they say the snow is awsome with a good base 3-4 feet of fresh.sorry didn't hear about boulder but I think it would be good as well.