If the light unit isn't too heavy, It may be able to be attached to the trim itself, without it having to go through the trim in to metal
Something like this
If you can get your hand behind the trim, you may be able to get a larger piece of plastic or metal with a hole in it that the clip holds on to
That way, it wouldn't compress the trim too much and would look like was an original fitment
I was wondering whether those lights above could look too much like grab handles. One wobbly older relative could soon get rid of them.
I'm going to see if I can get something to build into the covers for the internal roof rack, which I'll never use. I'd be happy to butcher them, as they're replaceable if everything goes wrong. I'm going to try and find a standard light with a diffused lens that takes a bulb. Then put in an LED bulb. At least then I don't have to re-fit anything if the LED goes pop.
The light in the rear quarter drivers side headlining boot area in my vehicle ( xtr etg6 December 2014 ) seems to illuminate the car very well in my opinion. Unless it's shielded with passengers in the back, I don't know.
I can appreciate for whatever reason people would prefer better lighting but is this rear light unit not fitted in all models ?