Max size difference between front and rear
 

I have a Trailmaster 150 XRS with 22-10-10's in the back and 20-7-8's in the front. I have a nice pair of Douglas aluminum billets with 25-12-10's for the rear. Can I put those on without any long term side effects if I'm mostly on mountain trails? Will the 5" difference cause wear to increase somewhere? I do have a set of 23-7-10's for the front but I would need to have custom- made wheel adapters to go from the 4x88 spacing to the 4x100 that the Douglas front rims which I have. So I have two options-go with the 5" size difference between the front and rear or have 4x88-4x100 wheel spacers made. Any thoughts or opinions?

you're gonna kill low end grunt with the 25s. that's a big tire for a 150. I have my daughter's on 23s right now and don't think i'd want to go bigger -- she runs all flatland, anything hilly and i think you'll struggle and possibly get into clutch/belt overheat problems. Up front different story, less rolling resistance, will smooth out the little stuff more, so no problem going bigger up there.