luggage rack

I was looking at getting the BMW base support and either the 350 or 460 roof box, but was informed by the dealer that the base support will of course work with the integrated anchors in the roof, but the roof box won't due to the longer wheelbase. Can anyone positively confirm or disprove this...

Does anyone know the screw/bolt size (thread size and thread pitch) for the luggage rack mount points on the 2009 335i Coupe? I'm contemplating anchoring a camera boom to a DIY bar that would attach to these points to avoid any possibility of marring the car's finish. Can't find the info on the...