Originally Posted by ktbb
in addition to asking what block are you going to make, my suggestion is that you clarify whether you really need to change the block size by only a half inch. It almost sounds like the block you need is to finish at 12 inches, which means it would be a total of 12 1/2 inches unfinished...or before you stitch it to surrounding blocks.
I've never seen a requirement for a block finished to 12 1/2 inches...however, 12 inches finished is a common size. Does your pattern clarify finished size vs. unfinished size?
I did a block called "Hearth and Home" and that block finishes at 12 1/2". I had made it for my Star Sampler then it was too big. It's an uncommon size but they're out there.