I ran 33's on slightly less than 4" lift for about a year with what I'd consider minimal trimming.
get 15x8s w/ 4" backspacing.
follow the cutting/folding directions here:
http://www.jeepin.com/features/bushwacker/index.asp
on the front floorpans, there is a pinch seam that sticks into the wheelwell, you need to hammer that over so it sits flat (it WILL cut your tires when stuffed/turning)
run flareless or install the factory flares up higher or use YJ/TJ flares (I used YJ flares)
extend your rear bumpstops 1.5" or so as well (you can then run a much longer shock and get WAY more droop, I was still running fairly short rear shocks in the pic below)
that's about the best pic I have of it with the 33's.
but my junk flexes just fine w/ the 36s that are on it now (w/ the same lift, but with more sag). there's a little bit of rubbing up front when turned hard, but I generally don't like turning hard as it puts too much stress on the u-joints
if I can do that, you can do 33's on 4.5" with NOOOO problems.