The extra loading on the suspension caused by the slightly wider inner track width is so small it is negligible. As you know, the wheel camber is set so that under normal loads the tyre will be sitting on the road surface evenly and squarely, but camber position changes slightly under suspension load and it is this camber position that could potentially cause uneven tyre wear. This issue, though too small to worry about, can be eliminated if the standard wheel rim offset is changed. Standard offset at the rear is 22mm. I went for new rims with rear offset of 35mm. This change in offset, combined with a rim that is an inch wider than standard, meant that the extra width is to the inside of the rim, rather than the outside. I could therefore use a spacer of say half an inch would restore the inside track width to standard. There is one thing to be mindful of when using spacers on a high performance car - it is wise to check the wheel bolts for tightness after they have been on for a couple of months, and again every six months or so. They have, in very rare instances become loose, but again negligible risk. You must use a good quality spacer with a central locating ring. Hope this helps!
Steve