I just checked out the site suggested above by Red100rt. Fascinating. It's the first time I realized that the stock BMW clutch discs don't have springs in them, circling the hub. All car discs I think I have ever replaced had those springs in them. And those auto discs were usually around $75. The discs shown on that site, developed with racing in mind, seem like the best idea. And at $375, although still unbelievably overpriced, they look like they would ease the strain on the splines considerably, and last a good long while. And they are probably still cheaper than BMW's stock discs, although I haven't checked. If mine needs replacing in the future, I think that is the route I will go, and get their spline grease also.