Here are a few photos of a mount I just built for my digital video camera. It is mounted on a Paratour helmet.
I started with a scrap piece of .025 6061-T6 aluminum, simply because I had that size handy. If I had to do it again, I think I'd use one layer of .063 instead. I cut 2 pieces about a foot long by 3 1/2 inches wide. Bending the aluminum over a table edge, I made the first 90 degree bends to form the platform on which the camera would sit. Once I had the two strips fitting reasonably well together, I riveted them. This is only because I started with such thin aluminum. Had I started with a .063 piece, I would not have needed to double this layer.
Once I had that done, I bent 2 pieces of .040 aluminum to form the brackets that would bolt to the helmet and to which the platform would be riveted. Once the pieces of .040 were bent to the approximate angle required, I cut them to the width of the platform - 3 1/2 inches - and riveted them to the platform. Holes were drilled through the brackets, then the brackets were used as templates to drill the helmet itself. Small nuts and bolts with nylock inserts were used to secure the mount to the helmet. Use a washer inside the helmet to spread the force of the nut and bolt.
A trip to the hardware store and I had the coarse threaded bolt I needed to mount the camera via it's tripod hole. I had to cut the bolt to size - it was a bit too long.
I used a velcro strap around the camera as a backup, and to keep the camera from possibly rotating, and thus loosening on the mount.
After finishing the camera mount, I proceeded with trimming down of the brackets to reduce the potential for line snags -in the worst case scenario. In the photos you can see how a line could become caught under the rear mounting bracket.
The image below, illustrates how the trimming was performed: