As someone said in a comment, we have a uniq chanes here to help alot of pepole so I encourages comments and discuss to make the best of the solution of this problem.
My idee is based on not having a "wave form" plate that sits on the roof as someone said "you dont have a standard "wave" on the shape of the roof". So my ide just sits in a hole as you can se from the pic. Only need some sealant around the edges.
Another idee is the "cap in the cap" as you can see from pic "coleled_third_vid". The green one is the light that goes in the cola bottel, then this is screwed into the red holder on the roof.
Why I have this, is that you can change bottle if needed and you dont need to go outside on the roof, all can be done from the inside. A spin off on this is having like a lightbolt fixture between green light cap and the red model. Just to fix the connention between the led and batteries.
The rubber wire is just for representative reasons, idee is to have the wire from the batteries in the red model and in one of the legs that holds the cola bottle.
The position of the batteries is something I also hade thoughts on. Insted of having the stright down. Having the position vertically minimzes the risk of the falling down.
One more idee is to have some more reflective materials on the saft that goes down the bottle itself. This may allow more light to bounce of the saft instead of being consumed by it.
So please comment and discuss about it.
Any questions about the idee or if something is not clear, just leave a comment or so I will happy answer.