Attached is a picture I took in the framing stage of the entertainment nook and the entry/hallway (left & middle arrows of the original picture).
I was not intending on removing what's there (d-wall) . Clearance would be a problem for a full half circle so I'm going for something less - sorry that did not come across in my original post. I was thinking of arches that start on the ends and meet near the middle.
Procon - the segmented arch bead looks like a probable match. I'll have to take a look.
What about the transition from the arch bullnose bead to the existing bullnose bead. Do I demo what's there and replace with a single strip (floor to arch to floor) or can I mud the transition enough to look good and not crack over time? I'm kinda lame in the sheetrock finishing dept. Great tips on using 1/4". I've walked through construction sites and seen them use that and/or 1/2" scored every couple inches.