For anyone using Onshape, I’ve put together a document containing configurable versions of all the default components of the AM14U4 chassis, including the bumper mounts and battery mount. You can copy and use these parts by linking or copying this Onshape document.
Everything should be reasonably materially correct. There’s also an example chassis assembly in there. If you aren’t interested in manually cleaning up all the files yourself, hopefully this is a nice shortcut.
Let me know if you find anything wrong, and I’ll do my best to fix it-- good luck to all teams!