In this pickle right now... I drilled a hole trough the body into the car hoping the interior panel would be right there and I could continue to drill through to allow easy access to the rebound adjuster. Unfortunately it seem the strut is very close to the outside of the car which does not create a direct path through the interior panel. I might have to take the whole interior panel off to determine a solution. Best case I make a hole which would allow a wrench with modified socket to access the adjuster. Any one else modify their interior on an R56 recently?
I had th4e extenders on the TSW sourced coil overs I once ran. They were all but useless. Had the jack up the car in order to be able to make them turn. The orange anodized knurled knob sure did look cool though. But the passenger side panel never did fit right again. Oh well, the quirks we live with.
Have you considered modifying a flexible socket drive extension.... One end would be attached to the valve on top of the damper, the opposite end would exit a hole in the interior trim panel with the adjustment knob attached.... Something like this.... McMaster-Carr