That seems like a very odd size for a finished block. I usually make 9" finished blocks. Each log is 1.5" unfinished, 1" finished.
Is there a reason why you want to paper piece this block? I've found that Judy Martin's methods for log cabins result in blocks that don't go wonky. Basically, the instructions are to cut so that log goes down the length of the fabric if possible (less stretch), use starch to avoid stretching, and (most important of all) cut all the logs to size before sewing, so that you know right away if your seam allowance is not right.