Just a quick but important point: if you plan on making an all-weather fitted cover for your dome, you need to abandon those "expert" calcs you find on-line. They are both useless and misleading. They are only useful at ONE temperature and ONE humidity. Period. They forget the real-world need to compensate for temperature and humidity, and these factors are far from insignificant.
As a real-world example, consider a 30 foot F4 dome. If you make a nice fitting cover that is carefully measured and cut out of 10 oz shelter duck at 75F and 20% relative humidity, the cover will DESTROY itself when it gets rained on. The cover will shrink nearly 2.5 feet at the base. All those stresses have to go somewhere, so they build up and then shred seams and zippers. Been there. Done that. Ouchies.
FYI: Canvas shrinks when it gets wet. A lot. Depending on the canvas, shrinkage can exceed 4%-5%. In no case is the effect less than 2%. So get a copy of the manufacturers specs for what you are using and engineer the necessary slop into your design. Understand that all canvas (at the thread level) is hydrophyllic... mystical coatings and "pre-shrinkage treatments" be damned.
Design accordingly, and understand the limitations of the fabric you are working with.