I had my Eken H9r mounted on the side of my helmet but I wanted a chin mount.
I have 2 versions, personaly I am linking the V3 version, there is nog much sticking out when riding without the camera.
Made a cast of the chin and then replicated it in Sketchup so it's not perfect.
Check out my video's, some are with the cam on the side of the helmet en some with the chin mount.
Should also work with GoPro.
I used ABS but PLA should work to.