I installed the bulkheads on my two builds after the deck & hull were joined and the hatch openings were cut out and it was a real PITA. I know some here install the bulkheads into the hull before joining to the deck (I believe ET has mentioned it is his method) and that is what I will do if I build another.

I imagine the trick in doing it before joining the deck & hull is to make sure the top of the bulkhead is properly sized so it doesn't interfere with joining the two sections but that shouldn't be too difficult to achieve as long as you are careful.

For me, getting a good bond on the inside tape (joining hull/deck) is pretty important. It's certainly a lot easier for me when I have a long expanse uninterrupted by bulkheads.

On my current project, I did install the behind-the-seat (curved and sloping) bulkhead before attaching the deck to the hull, as I reasoned that bonding the skeg control tube would be easier without the deck in the way. It was pretty awkward taping the inside seam in the stern, working through the oval hatch cutout. (It would be v. tough working through a round hatch opening.)

I've always found it pretty easy to bond bulkheads in place - if there is a hatch opening nearby. You can 'tack' 'em in place with a few dabs of epoxy putty, and then run a fillet later. Add bias glass tape if you are really concerned about making sure it won't move if you stomp on it with your feet.