For now, anyway :-)
First of all: I now own one double pulley! It was there, just beside the double flyer spinning wheel - it rather seemed like a "double" day. Until I asked for the other pulley... the dealer didn't even understand the question: why should he have a pair?
Anyway, it followed me home (even though the pulleys won't turn):
In the last post about double pulleys I wondered about Grenander's sentence "[...]with two pulleys on two axles on the same level [...]"
Jean graciously sent me a picture of this kind of double pulley(s):
Thanks, Jean - I had never seen such pulleys before, but apparently they existed even here.
Anyway, when I unearthed my folding CB to ready it for a demo, I decided to try to rig a "double pulley" simulation, to see if it would work with the crossed cord tie-up.
I thought I would just tie four cords over the castle, like this:
Half an hour later I decided I wasn't very interested, after all. (IOW, I couldn't get it to balance/work...) The horses went back on, and the demo went considerably better that it would have with the crossed cords...
Conclusion: hooray for countermarches!