Here's the updated version I just made with much more accurate cutting and drilling and then painted so they look nice. Lyres even a bit more narrowly spaced at 35mm.
Other hardware if you're curious:
Hosa MHD-4 5/8 F - 3/16 M adapter
Neoprene washers above and below bracket
3/8 hex nut
M3 lock nut and washer
M3 screws (included with lyres)
I didn't use 3/8 lock washers for the center mount, but instead used neoprene washers on both sides of the aluminum bracket which makes for a solid friction fit when tightened down with a socket wrench. You'll also see I wrapped tape around the bottom of the Hosa adapters with white marks that line up with corresponding marks on the front and back of the stereo bar for the angles / spacings I use. (The greenish mix is because I previously marked the bar with green Sharpie, and I just went over it with white paint marker.)
These are now exactly what I was looking for - very compact, fixed vertical angle, and best of all the total cost for both mounts came to under $70. I would say to others out there that if, like me, you want to step up to Rycote shocks but don't want / need the vertical adjustment, want to get away much cheaper, and don't mind a little work yourself, then I think this may be worth it. With better skills and equipment I'm sure you could make something even nicer, but this works for me.
Maiden voyage is this Saturday for an orchestra / choir performance I'm part of.