MauiSteve/Skyrider:
Yes I'm starting to get a much clearer idea of how this works - in that the lid of the spare kit is used as the cover when you take the kit out. I agree it's worth the $150 out and sounds easy enough to remove (and it's in the manual) so I can keep it out when I'm local, but put it in on longer trips across country.
The pictures Skyrider posted showed EXACTLY what I was looking for. I don't know if the trunk configuration of the M550 vs 540i would be the same, but I can't see why that part of it would change with the kit and lid for it.
You both have been very helpful.
Though, I'd much rather be driving my upcoming new car on Maui up to Haleakala than on the roads around here.
Thanks