A solution (I hope)
I picked up these "conservatory window cranks" or screwjacks in the UK.
50.00GBP!!! for the pair. (about $65.00 US)
They are double screwed so the total lift
is about 12" and there is a quick relaes pin at the top to allow easy disconnection for opening further.
They are chrome plated brass, not bronze but for that price
. also available in polished brass and "antique brass" finishes.
They were also available with permanently mounted crank handles but they stick down into my headspace. I'll shape up a nice crank for them out of aluminum
or stainless rod (whichever I find lying around first).