Fitting Inertia Reels

How would you fit them to go on the rear bulkhead? I want to be able to interchange roofs, and have them in an easy place where prefably I wont have to remove them.

Now I am a purist, we all know that, but surely inertias are a must have over statics? Im carrying my mates, girlfreind and famil tens of thousands of miles a year, and will always keep it original, but Im starting to beleive inertias are a safety must have.

I spent ages trying to find a good way of fixing inertia reels to an 88 s3. The only satisfactory method I found was with the hardtop fitted, buckle where it normally mounts, inertia reel on the rear bulkhead top rail, end of belt to bottom of floor base and the loop mounted on the hardtop using the appropriate LR brackets. That way the belt doesn't foul on anything and the inertia reels actually work.