The #1 bulkhead gets a large, 8" diameter hatch. Because access to this hatch will be tricky (one has to reach through bulkhead #2, between the mast and the hull side) I went with Seadog's lever latch model rather than a screw-in style. The good folks at Duckworks Boat Builders Supply like it, so I'm giving it a try.
Then I attacked Bulkhead #4. I punched two 5" holes in it.
It took a significant leap of faith to hack away at these parts, but that's all behind me now. I think... I might... be possibly... ready to go 3D. Maybe. More to follow.