The Wildman Jr. was also my L1 rocket, and the first altimeter bay I have built. I think it came out pretty well, and it has worked perfectly on every flight so far. The small diameter makes for some pretty tight packaging constraints.
I built it around a Perfectflite Hi-Alt45K altimeter, with dual redundant 9V alkaline batteries for power. There are 2 toggle switches accessible through 5/16" holes in the switch band. One switch applies power to the altimeter, and the other isolates the pyro charges from the altimeter outputs for safety. The switch access holes also act as the pressure equalization holes for the barometric sensor.
The electronics "sled" is made from single-sided copper clad G10 fiberglass stock, normally used for fabricating PC boards. 2 lengths of thinwall brass tubing are soldered along the edges of the sled to slide over the tie rods which hold the entire assembly together. The tie rods are 1/4"-20 stainless allthread rod. Each end cap has a small aluminum block attached to transfer the axial load to the tie rods, and recovery harnesses are attached via 1/4" forged eyebolts attached with nylock nuts.
The batteries are retained in plastic snap-in holders made by Keystone Electronics. The altimeter itself is mounted on 4-40 threaded standoffs, and the switches are mounted directly through the sled base itself. All wiring is done with 22 AWG stranded hookup wire, twisted into pairs to reject electrical interference.
Ejection charge connections are made through the bulkheads with miniature binding posts. I really would have liked to incorporate ejection charge holders into the bulkheads, but there wasn't enough room with a diameter this small. I opted for separate ejection charges in "single use" plastic canisters. Typical ejection charges are ~2 grams of Pyrodex "P" or Triple Seven, set off with a Quest Q2G2 igniter. The electronics sled is connected to the binding posts via 2-pin Molex connectors, to allow the sled to be moved between rockets without needing to disconnect individual wires from the screw terminals.