I'm going to provide a link to a photo album of the install that Jeremy Johnson at SpeakerLab, Seattle (206.523.2269) did on my car. Sorry for the first few pics which are camera phone.
LI STi-R on 2008 550i
The fronts LI heads are mounted using the small L brackets (now painted black), and the rears 3M taped to the lip either side of the plate. That surface is nearly perfectly level with little adjustment required. The fronts, on the other hand were pretty much a bugger to get aligned, and will require checking frequently I suspect.
The STi head is just to the side of the front plate (will likely have to install it, as much as I didn't want to).
The bumper was removed to facilitate mounting the beltronics head to the bumper support. The other big disassembly was the front dash to get at the retracting ash tray, for mount of the STi-R display and controls. I think this feature is one of the best custom touches possible in this car. Nicely done, Jeremy.
Wire routing was pretty straight forward - a firewall boot on the driver's side had a rubber nipple available to penetrate, and Jeremy routed the rears through the license plate light modules under the lid panel and into the hinge tubing.
I forgot to photograph the LI switch; it's near my right leg mounted on the lower panel beneath the steering wheel. Both CPUs are inside that panel as well. Cigarette lighter provided the power circuit. The beltronics speaker is just above the left-foot rest.
I'm looking forward to getting with some guys up here and doing some testing.
Obviously, I'm pleased and a fan of SpeakerLab's Jeremy and able assistant Ben. Kudos to them.
Let me know what you guys think.