I personally would stay with 1" bigger in the front (like stock) but if you must bigger in the back is better than smaller, it will just take slightly longer to engage.

You dont want to go smaller and have it engaged sooner or all the time.

The problem comes when the quad is on ground with full traction and no wheel spin, it will stay locked in for a short time afterwards.
The AWD system is actuated and sensitive to the rear wheel rotation speed.

Jim

 

I agree that the engagement would be delayed a little. What I would be worried about is when the AWD is locked in, the difference in tire size may bind the 4x4 system. Rear fighting the front and may cause premature wear in the front diff or trans. May not be a problem as long as the ground is sloppy or tires spinning at all four corners. But what about when you get to dry ground. Just my thoughts.

Steve Lubecki