I am on my phone looking at this so the calculations I can’t speak to. The door question has me trying to figure out what you are saying. 31” across the top should also be 31” across the bottom. Or were you asking about the lines that go up and down on the door? The tank shell between the bells, is about 70” which leaves you 6” between the doors and about an inch inside the welds for the bells. I would say that is ideal (for me). As far as the vertical lines of the doors I never measure them they are as long as they work out being. I start my door cut at 1” above top dead center and go down to 1” below 3:00 o clock so I can set my main cooking grate at the widest point of the CC.
I hope that helps
jm2cw
Making memories!