Good explanation about how to use rooms and walls for curves! I didn't know the auto-dimensioning plugin could fill in, I have never needed it and I should investigate it's extended features.

But... check out some images of stadiums. Every stadium uses wedges like I created for the corners. So far I haven't found a stadium that uses rounded corners. Maybe there's a conference presentation hall that uses rounded corners for seating but I doubt it. The construction is more expensive and it doesn't increase seating efficiency. A rounded corner for seating does look good though!