This is a test practice piece. It’s a simple diamond pattern insert into a three sided panel, as it would be in a seat back.
I realize that when I sew foam and stitch the diamond pattern the insert is smaller. Yet presuming I just take that out of the picture if the outside piece has a window the same size as the insert plus a half inch seam allowance (1/2” inside…so if stacked face up there’s an inch overlap) yet when used it together the outside piece appears too long across the top.
If the outside piece was three parts two sides and a top I can make it work but apply those same measurements to a one piece outer.
If my finished pattern is 10”x7” I add half an inch seam allowance around it so 10.5x7.5. What size should the hole be in the outside piece to fit seam to seam to fit the pattern. 9.5x5 should give me a half inch to sew to the insert but it’s wrong and I’m not sure why. Any help is appreciated.