Nice write up and i may consider doing this. but why not just use a bolt that screws into the tow hook opening? You could do some trial and error with length and just use a nut on the front and back of the plate holder for the correct distance out from the bumper. Maybe for version 2.
328| ZPP | ZSP | ZCW | CA | 6FL | NAV | XENONS | 18x8.5 VB3s ET30/25
2011 Jet Black
535i xdrive | ZPP | ZSP | ZCW | 6FL | NAV | 331s Square