[DMXF]

I will add to the speculation with a general observation that the design at that area is so poor that I suspect it will be hard to completely eliminate the cracking for the more extreme usage applications. Think of it as a cantilever beam where the fixed end where it meets the center thick part of the track has a geometric discontinuity with reduced bending stiffness (look at how you even lose the inward wrapping flange there). Changing the outboard end constraint (more rigidly tightened bolt) or even material strength will only have a marginal effect. I assume these tracks are not heat treated after forming, so there probably isn't that much difference in the material properties for them to be formable without cracking. Also, you can only get the bolts so tight, as I recall you're going through the carpeting and the original square tubing there crushes easily. The best that can probably be hoped for is incremental improvements across multiple attributes described that may add up to enough improvement to keep the problem at bay. The ultimate solution may be something like a stiffening plate that bolts under the track with flanges that wrap up on each side to dramatically increase bending stiffness, combined with some way to capture the upper corners of the track on each side. This way it could be removed for when cars need to be aesthetically correct like going through the auction block.