You guys are overthinking this. Go to http://www.desertdomes.com/domecalc.html
If you build an odd frequency dome, there are instructions to build it 3/8 or a sphere, or 5/8 of a sphere. If it is an even frequency dome, the instructions are for a half sphere.
Seems logical to build enough struts to do the whole sphere, and bolt it together. Build a 5/8 sphere, and just keep going when you get to the ground. Or likewise for a half sphere. You will have some doubled up struts if you just take the half sphere list and build two sets, likewise if you add the 5/8 list and the 3/8 list for an odd freq.
I built a 3 freq dome from this site and have used it for 6 years now. The beauty of the odd freq. is that the bottom section of struts is perfectly vertical, as the equator of the sphere is halfway up from the ground in that bottom section. This way you get more usable space inside. With an even freq. the equator is at ground level when you build it half sphere.
I have seen several on playa of the exact size as mine, as the longest strut is half of a full stick of conduit, INCLUDING the extra 1 1/2 inches you have to add to the 'hole to hole' dimensions given in the chart. I imagine however that you would want to build one quite a bit smaller if your going to build a full sphere. My radius is around 11 ft, 22 ft diameter, with ceiling height (5/8 sphere remember) at around 13 ft. Much to big to build full sphere, not to mention the idea of tying it to the ground........