Update: Last night I bit the bullet and cut it up. I drew pencil lines first to make sure I could get all the blocks in. I'm glad I did, because I didn't like the first set of lines, so I drew a second set of lines. Rotary cutter didn't slip, so I got all the blocks I need. Then I sewed each block to its partner 9-patch block. Little progress, but it's progress.
Thanks for the kind words, everyone!