When I installed my GXP STB, I remembered that the stock strut tower bolts seemed somewhat short. Well the other day I was checking the brakes and while in the wheel well I noticed that the stock bolts do not fully hit all the threads in the strut mount (caused by the STB bracket thickness.)
To resolve this problem, I went and picked up (6) flange bolts (M10x20mm x1.50 thread Grade 10.9) from Lowes for about $3 each. Installed 'em in a about 5 minutes. I rechecked in the wheel well and the longer bolts now hit all the threads.
The stock bolts weren't cause any problems, but I just didn't like the fact that the bolt wasn't making full contact with all the threads. I feel a little better now. I thought I'd share.