Yeah, welcome back, Slow.
I'm glad this thread came up again. I almost forgot that I had taken some pics of the spit forks that I made.
The spit is probably 1/2 to 5/8 inch square. The prongs of the fork are each bent 90 deg's, two ways, so that they form a square when joined together.
Thumbscrews lock them in place on the spit.
I made a wider set of forks, too, but they aren't ever used.
This is what I was referring to about turning the bearing area of a square spit round.
This is the bob weight from mom's gas grill rotisserie. The slot in the bail pinches between the handle and a wide washer on the threaded hilt of the spit. By rotating and/or sliding the weight in or out you can adjust the balance of the roast. Kind of overly complicated for a simple camp setup, but it gives you an idea of the importance of balancing the roast on the spit.