An additional reference that might be of particular interest regarding self-supporting rotegrities and related structures.
Reciprocal Frame Architecture by Olga Popovic Larsen.
In particular, some formulas in Chapter 4 starting on page 37, regarding some of the angles and lengths around the intersection of beams. In a general sense, the hub. Perhaps some of you are already well aware of these calculations and/or could derive them on your own, but it does save time and effort when one can "cookbook" from work already well done.
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