We are using our summer to experiment with custom gearboxes and building our first west coast style drivetrain.
Here are some pics of our first custom gearbox, toughbox innards with custom sideplates:
We currently have on order a frame and gearbox plates from Team221.com:
http://team221.com/viewproduct.php?id=108
When the plates arrive, we plan to machine lightening features to remove even more weight.
We are finding that the custom gearbox route is an interesting balance between cost, machining time, and design flexibility.