Frankie,
RE: Bumping your head -
Yeah - there are several types of domes... oblate, spherical, etc. that may alter the curvature of the dome.
Or... you could add a 4-foot (or 6-foot) stem wall - which raises the straight portion of the wall off the ground - prior to its' curvature.
Actually - I've been in several of these domes, and if it's done properly, and the furniture arranged properly - you don't even have to worry about the curve... unless you play for a basketball team and are over 7'0" tall. *grin*
Like someone else already pointed out... they are bigger on the inside than they look.
Regards,
Jim TX