1)
Why is it written Komah, and we pronounce it Komas?
1.
Radak: The Kesiv is as if it is known (the height of what was mentioned (without Semichus), even though [really] it is Samuch. We find like this - "k'Eifah Se'orim" (Rus 2:17). The pronunciation is proper (Samuch).
2)
If the circumference was 12 Amos, how could they be only four fingers thick?
1.
Rashi: The middle was hollow; the pillars were four fingers thick around the hollow.