What size do you run in the front? I run 22's all the way around, and I got 22" paddles for it as well. Seemed to be fine. But I saw one member on here at the dunes with 9'' rims on his using spacers and he had 20''s, if not smaller. Don't worry about looks, worry about operability. Either size will be beneficial. Just determine what you want, how many paddles, and the shape of the paddle. I am running 8 paddles/tire due to having more HP than most, and they seemed to hook up fine. I've seen others running 6 with out any problem. I'd say if you have 20 or 21 on the front, go w/ 20 in the rear, but 22 or 23 in the front, go with 22's. or go off from what size rear you have on there right now.
2008 700xx; Power Bomb header with power core 4 exhaust, Power Programmer III, pro armor nerfs, prm products control front and rear bumpers and full skid, 10" ITP rears, ITP Baja's fronts, RZR 2's all the way around, Uni filter, 13t sprocket, CCP steering Damper, DS450 shock swap, Dual Gasser Throttle, bar risers and Moose barkBusters. 730XX kit plus other engine mods!