Yup, the lip sits inside the F-1004D bulkhead until you rivet the side skin on in Section 29. My section 26 plans were the most recent copy which resolve a lot of the ambiguous dimpling instructions from earlier - on page 26-5 in my set the plans say to dimple all the #40 holes in the web of the F-1015A ribs. These holes would be difficult to dimple after the ribs have been attached to the rear bulkhead, and my side skins were final sized already so I didn't need to drill those holes. Note that you don't dimple the holes on the flange of the F-1015A rib that sits inside the F-1004D bulkhead.
I did find a hole that I had to match drill farther back, I believe in the F-1018 rib. So I had to dimple that with the cleaveland pop rivet dimple die set, but it wasn't too bad.
Alex