Somewhat tangent to Gutbuckets lead,...
Is there a particular reason to stay with that 5/8-27 thread?
Have you tried to see how a 3/8-16 thread rod connector ferrule might fit in there?
A 3/8-16 thread rod ferrule cross-sectional wide profile comes really close to your specified dimension of .47", at its widest mark. I'll dig out some calipers and see if I can get a better measure.
I use a whole series of adaptors made from this same thread pitch thread rod, with ferrule connectors and jam nuts.
The Manfrotto Mini allows these adaptors to pass through the clamp, lengthwise. It has two set screw points, and, locks the adaptors securely. From what I see of the Windtech, it would have similar capabilities.