Trying to widen my stance...
I ahve the spider trax spacers. with the stock 16inch steelies the edge of my tire was just a bit outside the fender. now with 35x12.50, I think i have about 6 inches of rubber sitting outside the fender.
4.5" Backspacing will stick out around 2" further than stock. I believe the wheel offset will affect that too, but I still don't really understand offset. I believe the Spidertrax spacers add 1.5".
I still have the stock rims and tires on my Rubicon. The 1.5 inch spacers will put the outer edge of your tire even with the fenders. If you want to see first hand take a tire off and hold it one and a half inches from the hub. I have spidertrax and no problems.
Here's mine with 1.5" Spidertrax spacers:
I've had the spacers for close to 10,000 miles and no problems. I drive a fair amount on winding gravel roads which vibrates everything and tends to knock things loose. I haven't had to tighten them yet.
The important thing to remember is to check them periodically (every time you rotate ~3k-5k miles) and use red locktite on the stock lug bolts to secure the nuts holding the spacers. I tightened the spacer nuts with 105lbs of torque initially. I check them at every tire rotation by setting my torque wrench at 95lbs. That way, I don't break the locktite seal and I am assured that they all have at least 95lbs of torque. The wheels go on at 95 lbs also. I've never seen anything budge.
I think it improves handling, especially on tight curves.



