Has Sachs drum brakes which are adequate but for my hilly area I greatly prefer disks. I still have the box for the Dragonflyer and the shipping cost will depend on how far it needs to be shipped. Just thought I'd pass this tip along. They really spread out the pressure on the metatarsals. It needs to take a standard 7 or 8 speed cluster in the center, allow either wheel to turn faster than the other for cornering, drive the slowest turning wheel, and allow for brakes near the cluster to keep them away from the tire slop.
Light weight is a definite asset.
More simple than a diff to construct. There there some very high quality components available that combine a sprag clutch and ball bearing in one, e.g. the Stieber CSK models. These are quite costly, but definitely preferable to the freewheels used in bicycles because there is absolutely no slack in the uptake, which is most important in a diff. About the same size as sealed roller bearings. They have no keyway or spline, so you need to machine the shaft and housing to a very precise force fit.