Our solution for mounting altimeters and an action camera, and all associated hardware (switches, batteries, etc.)  Holds up to 2 altimeters, and one action camera - GoPro or similar.  No heavy and unnecessary all-thread.   Great for the experimental payloads you've been wanting to try!  Laser-Cut plywood parts glue together easily and mount in our 5.5" airframe tube or 5.5" coupler tube!