The hub is built up by cutting individual pieces from plywood and laminating them together. The issue is consistency in measuring the 120 spacing, and getting accurate cuts. It seems inevitable to have considerable overlap as the layers are glued together, leading to lots of sanding. To solve this problem, I glued the central hub together first, then cut a polygon on the table saw. Very slick. Unfortunately, I either made a measurement error or my original table saw mitre guide failed to cut the proper angle (I have since bought a new mitre guide). So, the legs are not precisely spaced at 120 degree intervals, but at least little sanding was required.
The second issue in fabricating the Berry design it drilling straight and accurate deep holes in the hub for the tripod leg bolts. To solve this issue I used two matched blocks of wood to make each lobe. These were drilled with a forstner bit then glued to the polygonal hub body. I used a biscuit joint for strength, and after the top of the hub was attached I added an additional dowel pin. I found this variation to be extremely successful.
For added rigidity, I upsized all of the hardware from 5/16” to 1/2” bolts, all in bronze sleeve bearings to eliminate wear on the wood. I hardly every use 1/4” in my projects anymore.