I didn't say anything about backpacking. Dome tents give more head and shoulder room than A-frames regardless of the height, floor area, headcount, or phase of the moon.

Eureka's A-frames were great in their day.

You'd be much better off with a high quality dome tent, or if it doesn't need to be self-standing, the tunnel tents (not sure if that's the right term) that are so popular now in Europe have great space and are very easy to put up. These are the ones where you stake out the front and back, and the frame creates a sort of tunnel. They're not so popular in the US yet - cabin tents seem to be making some kind of comeback, but Eureka Canada sells some of these.