Monaro high level brake light fitting

[KMud]

There are a few threads on removal, but probably a daft question, how much effort should it take to refit? I'm wanging on it pretty hard, but struggling to get the tabs to re-engage - doesn't help that access is very limited, so hard to get purchase and see what you're doing.

On a positive note, apart from the floating brake light, my speaker rings seem to fit under the shelf carpet

[KMud]

Tried again with the wife looking at what's going on in the boot, the wedges go through the slots but don't bite. Either I'm doing it wrong or I've gained a bit of a hump in the rear shelf carpet which is popping the brake light back out.