Sounds more like time for a big drinky instead of a little one
123D design should be able to handle all the mods for the lobed shaft based on a quick look, I'll qualify that by it's on my todo list but I've never used it. I'd have probably used 100% infill and a dremel or round file, but design was more organic when I studied it. We used organic wood tools, with dark marking cores, not this new fangled computer stuff.
For the D shaped shaft, use a round hole and a setscrew that hits the flat. Drill a hole in the collar for it. I think screw holes for collars were somewhere on Art's very long list, but I'd trade them for webcamed faces (not sure about eyeballs).
Yeah, stl is not a great format, don't understan
d how it became so popular.