Your forcing me here to post some pictures!
Here is a picture of my altimeter bay. It is a coupler tube. Each bulkhead consisits of:
1- 1/8" ply bulkhead inside coupler
2 - 1/4" ply bulkhead outside with O-ring groove
1 - 3/8" ply to connect the U-bolts to
Left to right:
The left bulkhead is removable, and has an extra o-ring to seal. Next are the ports, CA reinforced. The right bulkhead is epoxied on, so no worries about gas leakage. Then are some 6-32 brass wood inserts with 6-32 button head hex screws to keep the bay in the rocket. There are 3 and they are equally spaced.
The bulkhead is connected with a piece of 1/4-20 steel threaded rod run in the center of the bulkheads.