Yah, there's not a good way around this problem. If you attach the cladding well enough to survive contact with a rapidly spinning tire, something else will break. It's like a chain: strengthen the weakest link and then the 2nd weakest link will break. It's better to engineer the situation so that the forces applied are such that you aren't pushing parts to the breaking point.
The only long-term solution is going to be to stop the tires from contacting the body.
A few options:
- Get a fabricator to build a custom, one-off lift kit for your car.
- Cut your fenders back and/or get some flared fenders that will clear the wheels/tires (probably custom).
- Buy a different wheel/tire package that will actually fit.
Going from +50mm to -25mm offset is a pretty drastic change and I'd be surprised if it handled and rode anywhere near as well as it used to. How much steering wheel kick back do you get when you hit a bump with just one side? You're putting extra strain on all of the joints by doing this (farther out = longer lever arm). Also, your scrub radius has got to be all kinds of wacky.
Honestly, if I were you, I'd look into getting something closer to offset (+38 mm wheels are readily available) and then experiment with spacers to see how far out you can push the wheels before they start rubbing.