The light kit I'm using came with a strap on helmet mount and a tail light meant to be attached to the seat post. Using a rear rack with a bag on it blocks the use of the seat post. And I decided I like the headlight on the helmet better than on the bars.

So the helmet strap was tossed just leaving the light mount and tilt piece. Screwed it directly onto the helmet and cut off the screws nearly flush with the inside of the hard shell. Then drilled a hole in the rear of the shell and mounted the tail light. Then reinstalled the hard foam liner and all is good. Headlight is on solid, so is tail light. Although I think it looks kind of dorky. But it works great. I take off the headlight for daytime riding.

This works the best for me because I don't have to get dedicated lights for each bike. Especially as I have 4 bikes and 1 ebike.