Greetings, for those who want to find a good DIY for installing a radar on your M5 this link was perfect -
http://www.2addicts.com/forums/showthread.php?t=998321
Everything was right on, except for the Blendmount part for my M5 -
Blendmount Beltronics / Escort Radar Detector Mount (Escort MAX) for BMW. Mount. (model: BMX-2017)
MirrorTap MTX Series Radar Detector Power Cord With 2 Amp In-Line Fuse, Military Grade Taps, RJ11,15" Long
Hope this helps for anyone interested.