A Connection That Makes Sense
I want the rangefinder to be easily removable from the helmet. So, I’ve come up with an idea to modify the shaft. Let’s see if I can make this work…

Since this will require some precision fitting, I need to make sure all of the parts are connecting correctly. The screw needs to be counter-sunk into the plastic plug.

I used a curved blade in my exacto knife to create the angled edge…

That should work.

While I’m working on this piece, I may as well remove those square corners. They no longer server any purpose.

I used my dremel to remove the corners, and also rounded the main edge a bit.