John,
Thanks for your kind reply. I replied earlier but for some reason it wasn't posted - doubtless my own fault.
Was there anything except the bow armature connection to the centre span armature that your son designed in SolidWorks that you needed to design yourself?
If available I'd love a copy of the SW files you made.
I've seen the other thread also and got some great input there from Jeff.
Best regards,
Marc.