Do you wheel with buddies? I'm really concerned about what may happen if you were out on the trail alone. Not just the added stress on the suspension, but your OEM lugs - the bending stresses increase with the wheel out that far. And remember, you'll have to torque and check three sets of lugnuts, effectively - those on the wheel, those from the outward spacer to the inner, and those on the inner spacer to the hub. I'd do that every 500 miles as a start, then work your way up to every oil-change if they are staying tight.
Also - anything keep your tires from pushing up into your fender-edges? I'd hate to see the tires spinning off road, then shoved up towards the edge of the fender, and having the fender cut the tire down the middle.
If you start hearing a rubbing sound while driving on flat ground, get the bearings checked out - eventually you will feel the truck sorta get shifty as you turn. Bad bearings = wheel runs away.