At first I was a bit at a loss for what might be useful, but after trying a bunch of different templates it came down to two. The first one was just to locate the intersections.
The other template was only for laying out
the fishes. While the chalk marks were fragile, with a few different colors of chalk to make the new marks easier to identify it went pretty smoothly, if slowly.
I realize that people who sew much don't need many hints, so I'm taking a break and letting Chicken finish this up.