No, I am not running spacers. I rub a little bit in the front when at full lock, mainly on my control arms, and a little on my upper spring perch. It's mainly on one side because I have the stock front trackbar and it pulls the axle to one side, making it closer. If it was centered, I bet it would barely rub, and I could just add a small washer to the steering stop to keep it from rubbing. Once I add aftermarket control arms, I don't think it'll rub the control arms anymore though.
For the rear, you will have to run an aftermarket trackbar or a the OME trackbar bracket because when I didn't have it on, my tire was about 1/8" away from the upper spring perch on the driver side with the 285s.
If you get the 305s I would definitely run spacers though. The clearance on the upper spring perches and the tires in the rear is still pretty low, so the 305s would be even closer to rubbing, although it worked for a little bit on my 2" lift.
EDIT:I just remembered you have a Rubicon, so your flares will stick out 1.5" further than mine (3" vs 4.5") so even with the wheel spacers on the 285s, you should still be under the flares. The 305s, should only stick out a little bit with the spacers.
When I go home for lunch I'll try to snap a pic of how far out the tires stick from the flare. It may be a little off, since the front is on jackstands right now (I broke my Jeep