Front Bilstein insert gap

[Rusty]

The answer, as per Lago Blue above, is that the top of the damper body engages with a recess in the top nut, such that the nut supports and clamps the damper body inside the strut. I've just test driven the car and it seems to be fine, including some speed bumps at 20mph... with Hnr springs...

[90/90qs]

Since a long time back, I seem to recall even Mance suggesting a few rings of duct tape around your bilsteins and a drain hole in the housing. Pretty much every quattroworld user on the 80/90 forums running bilsteins subscribed to this method.
I just replaced an old hand me down cartridge a few weeks ago and used gorilla duct tape. Great stuff, it ain't going anywhere :-)

[Bowie69]

I replaced some dampers and found, but not the same issue -the replacement caps would not screw down far enough to clamp the damper down -I used the old caps in the end which worked fine, they weren't too bad nick after all

This was on a 7A, so probably smaller dampers, but still.