Traded my '06 E90 in on an '08 E83 about a month ago because I needed more room. New to the forum but have been browsing around for months as I was looking into making the transition. I installed a hitch which I will use most of the time but I wanted the ability to put bikes inside the cabin for races/rides that are farther away and room wasn't a concern.
This was what I came up with, fairly simple and clean, turn knobs to adjust or remove if needed. I also inserted teflon pads where the crossbar meets the built in rails for smoother sliding and to avoid metal to metal scratches/damage over time.
Pics below:
-Jason