I have the schroth harnesses installed and the mounting pieces are indeed bendable but still beefy enough to do the job. I would study the design, bend once (to reduce any metal fatigue from bending) and install. If you need to see the harnesses installed in another MINI, that might help let you see how things fit before you bend.

Once bent the mounting hardward will work fine. I use my Schroths for autocross and track.

 

I just bought a Schroth-seems to be the best solution if you don't want to go the full route. It really holds you in well, and certainly seems substantial enough for autocross and the occasional track day-I'm going to get another for the passenger side next. Didn't come with instructions, but Soloracer has the pdf on their website-only real tools needed are the Torx T50 and metric (15/16/17 mm) socket/wrench set. I like the ability to remove it quickly as well.
Phil

 

did you buy the ones that clip or the ones that install semi-permanently?