Has any thought been given to using a catenary curve for the dome. It is structurally superior to a spherical dome. An egg is a perfect example of two different catenarys. Properly done, a catenary dome could be paper thin and still be very strong as all of the downward forces are transferred laterally and down into the dome curvature. There are no forces trying to push the dome in or out. This could reduce the amount of material required tremendously.
I am doing "Nubian" arch domes. I.E. 21" dia horizontal internal base. The vertical will be from a 3' offset from center.