Spoke with a few wheel manufacturer/re-sellers (was told not to mention their names or initials but they build OEM wheels for all car manufacturers). Although not recommended they had no proof it will cause an issue, if the washers are all the same height tolerance (and 1/16" or less) and the wheel is still mounted hubcentrically. One was a wheel specialist that will repair and refinish wheels he has see lugs break and wheels fall off due to height mismatch on the spacers and improper torque.
Most of the forces of the road/track/trail hit the wheel and back to the suspension through the hub axially hence the hub centric designs. Laterally (flexing the wheel between the lug bolt holes where the washer will not be) there is possibility to do this and it goes back to the tolerance in height of washers, diameter and their materials. Some wheels have material that touches the hub of the rotor and others do not be design. I found a picture of the back side of a couple wheels next to each other to show the face that touches the hub, some are full contact others not.
I also tried downloading the SAE manual about wheels and all I could find in it stated that no spacers are ever recommended unless placed there by the original manufacturer. Be it washers or full circular spacers.
So in conclusion: No spacers/washers are ever recommended. If you want to use spacers, your choice but insure you have at least the diameter of the lug inside the lug nut (1/2" engagement on a 1/2"-20 stud). Washers can be used but you need to be diligent in the thickness choice to insure hub concentricity. Always check the torque spec of your wheels especially with spacers of any kind as any movement of the wheels on the studs will fatigue the stud and you could lose a wheel and your life.
I've read all sorts of on-line smart people..... who use everything under the sun for spacers and some with good results and some with bad. Some even claim that the best thing to do is grind some material off the caliper instead for clearance........ Watch those used cars you buy. Your call in the end.
I will stay away from spacers for now on this Jeep. Hope this clears things up a bit as i know it was a learning experience for me. Thanks to all the contributed.
'06 XK Inferno Red Crystal Pearl/Gray Leather