I recently retrofitted roll hoops on my Z, It's an excellent DIY.
just make sure you get the correct parts. There's slight differences between pre facelift and facelift parts, and obviously between cars that had roll hoops and cars that didn't.
Basically, you have to swap the whole back of the interior trim.
The lower/back trim i got had holes on it so i only used the upper/outer trim bits instead of the whole thing (see in the back of the bottom of my post) They screw in just fine, just don't sit 100% flush. They don't squeak or rattle either so i don't really mind.
The only differences between roll hoop and non roll hoop enclosures are the plastic tab and metal bracket inside which is there to snap the upper trim onto, and the rubber seals on the side. This is why it's recommended to buy the whole thing.
Here's a picture of what it looks like.
It's just melted on on one side, other side is held by brackets.
I adapted my non roll hoop case to accept roll hoops by melting those trims off and simply swapping out the plastics and brackets.
(i did this because the enclosure i got had silly speaker holes on it aswell.)
Here's the finished job.
Note: my kit didn't include the small center lid

I'm going to build one out of fibreglass because i REFUSE to spend 200 dollars on one from ECS.. noone's selling them used cheap either.
Also!
Early 96 Z3's cant be retrofitted with roll hoops as they don't have the mounting spots, the brackets will need to be welded on in order to accept the hoops.
Cheers everyone
