The complaint: The traditional rod and lid bay made sense when electronics were large, as it uses internal volume efficiently. Now that electronics are smaller, it has some limitations. The altimeter and battery, which are checked every flight, are buried deep within the bay. Downloading from the altimeter or charging the battery requires taking apart the airframe and dealing with rigging. This is both time consuming and a source of errors. Since the altimeter is fastened deep inside the bay, moving altimeters from rocket to rocket on launch day is hard. This means that either you buy many altimeters (expensive) or have fewer launches Because the altimeter bay is part of the airframe and needs to be openable, it becomes less stiff. The upper bay, an open tube, is pinned to the avbay coupler, an open tube, which is stiffened only by a loose-fitting lid (compared to a fixed bulkhead). If you take a DD rocket and bend it lightly, you can see most of the bending happens at the avbay joints. All these limitations result from components needing to perform multiple functions: The avbay lids are also the rigging anchor points, the nuts that open the bay also hold the airframe together, etc. Proposed resolution: Driving home from a launch it occurred to me that it's easier for me to change a motor than change my altimeter programming. Why not use the same system for both? Changing a motor doesn't require taking apart the airframe or rigging. Why not use the same system? It's cheap, simple, and uses COTS hardware Here's a little sled with a tiny LiPo, EasyMini, and MW3 screw switch. It's now a cartridge Cartridge with charges attached Two motor mounts here. On the right, 24mm motor mount. On the left, 29mm "motor mount" the length of the coupler. Here's the airframe and cartridge (Tried using acyrlic color shift paint. Doesn't look so great) Load the altimeter in the mount like a motor, screw it in, done. After launch, unscrew altimeter, plug into computer to download data, pop the cartridge into another airframe, wire up new charges, etc.