That looks a perfect fit!
I was reading a bit on the new owner of the RH brand site, and they stated something interesting. Apparently, very early French (read Stronglight) tapers got copied and actually became the JIS we know today. Campag came later, and developed there own standard which became ISO we know today: obviously driven and popular by the concept of a complete working Gruppo the French never properly got to grips with (ever....).
Your experiments actually confirm this when you bolted and dry tested the Shimano crank, and me for one, I see what you are doing is proof looking at this and a few posts back. First time I see it with real hands on
This is why I think this thread is so superb. Really getting dirty and not just showing off a finished RH exotica built, but going through the twists and helping us to understand what mechanically is actually going on.
What I do know for fact, and I think that was what you are referring to, Stronglight went through many transitions legally and of course had to follow fashion. It's amazing that they actually have little idea exactly what there ancestors did, and it is documented elsewhere, they did inbetween tapers of ISO and JIS. I have written to Stronglight and they said they can't really help with the vintage stuff.
For me, this so ironic - the inventors of the square taper, actually got buffeted about, put in corners, adapted, dangling to survive which they are barely doing. Today I think they only do JIS so a full circle.
I could never foresee RH had the means to actually make a crank themselves at this period (no way could a man in a workshop type of thing compete what was happening in the industrial centre of St Etienne with this new material) and like you say yourself they are very similar to the Stronglight. I understood from the French forums that the AL cranks gradually got beefed up with several succent tweaks.
