According to Haitz's Law [1], Flashlights are not going to decrease in power anytime soon.

When in a tent when camping or in many other situations, you'll need it a little less bright.

The slit is closed at the down end of it to prevent and make it easier with warping.

Maybe it could be improved by adding a little ring on top so that t can be hung from the ceiling.

[1] https://en.wikipedia.org/wiki/Haitz%27s_Law

Measure your lights diameter, and make up your mind over the other parameters, compile, render, export as STL.

Print, break the little bridge on the down end of the slit, put it on the lamp, enjoy.