Just noticed this now, congrats on a successful DIY!
Sorry for not remembering the center bolt on the starter was a T30.
I have to admit I thought about it, but double checked on realoem.com... And it lists it incorrectly:
http://www.realoem.com/bmw/enUS/show...diagId=12_1200 - Part #3 =
http://static.schmiedmann.dk/Product..._89577_big.jpg
Regardless. Good work and a helpful well written DIY that will come in handy for many folks as the years progress.