So i wanted to start using my RunCam2 4K camera on some smaller rockets. This cam, although small, is rather bulky to mount on the side of a rocket so I set off to make one that could mount internally. I've made 2 versions of this for standard size body tubes, BT-70 and BT-80. The BT-80 camera mount is set at 45 degrees while the BT-70 is set at 25 degrees off vertical and designed to make sliding the camera in its place easily while limiting how much of the camera protrudes from the side of the rocket and maintaining a decent viewing angle.
There is a bit more mass on the "back" side of the coupler/mount so as to help keep the center of mass along the vertical axis as close to the middle as possible when the camera is in place. i put a lot of hole cutouts wherever i could to help keep the weight down. The BT-80 weighed in at 49 grams while the BT-70 came in at 55 grams as it had to be taller to fit as much of the camera inside as possible (This weight was with Siraya Tech Fast Resin, results may vary depending on your Filament/resin. The FWD and AFT shoulders have 4 rows of cutouts and then 3 x 5mm holes in the middle to be used with plastic rivets so the camera could in theory be placed on existing rockets.
I also made a couple of "cups" that can be slid into the bottom and glued in place if you wanted to attach a shock cord/parachute to this piece. I use this mount/coupler with a4" Body tube on top of it attached with Rivets and a nosecone. The entire top end of a rocket interchangeable with any other rockets by just removing the shock cord from the nosecone of said rocket and attaching this entire piece in its place. Picture is worth a thousand words so see attached video (https://youtube.com/shorts/HeNh2FP4TU8) on how i use mine.

These are the removable plastic rivets i like to use: https://www.apogeerockets.com/Building_Supplies/Misc_Hardware/Removable_Plastic_Rivets

Please do share your creations if you try it!