Hi Mick,
Have been following your posts with interest.
Your approach is to be commended, and has resulted in myself having a new look at couplings.
Part of my job is to design mechanical 'things', and have never seriously sat down and looked at couplings in my model boats.
Your coupling allows for miss-alignment in all planes, and with the addition of a sleeve/spline on one of the shafts could also allow forward and aft adjustment.
Will be looking into your ideas, if you don't mind, with a view to replacing joints in all my boats, ranging from 12" to 48".
I generally "steal" from everywhere in building my boats, so to borrow from model car development, if it improves things, is acceptable.
If the old "dog-bone" style coupling had the pins each end at 90degrees end for end, it would have been a step in the right direction, even the 'Huco" double couplings have been designed for only one plane change in direction, not mis-alignment .
Keep up the good work, and keep posting please.
The world needs creative thinkers like yourself
cheers
vnkiwi