https://cdn.shopify.com/s/files/1/06...47687512016358
According to Donna Jordan tut here, her 9 patch square is made from 2 1/2 jelly roll, so her 9P should be 6inch finished ( with seams to JR strip) She cut her strips 10 inches I think it said. So 4 inches more than your center square panel is what I’m understanding but using the 2 1/2 in black sq too. According to that you would cut yours 4 inches more than your 10inch cat panel square or 6 inches longer than your cat panel square if you don’t use a center stone like her black here. At least that is my understanding.
if the link doesn’t work just go to Jordan fabrics site and look at free patterns. It’s a runner but that’s all columns are.
https://cdn.shopify.com/s/files/1/06...47687512016358