Thank you tw.
If I used the 30-inch circle, it would make the gun about, Left barrel skeet, and the right barrel, full. (the gun is an IJ "Skeet-er" and the left barrel is for incomers and is the tighter of the two chokes.)
The left barrel does seem to be too open to shoot the middle stations at Skeet, so, maybe cylinder choke is right.
Pete