'If I add blocks now, I won't be able to sgueeze the bow and stern
together to match deck. "

Jim, If you dry fit the deck onto the hull you'll probably find that they fit pretty well at the ends with most of the the misalignment at the center of the boat so I don't think the blocks will interfere with alignment. At least that was my experience.
I carved (bandsawed mostly) some blocks from some very lightweight 2" thick pine. Could just as well have been cedar. The blocks didn't fit perfectly as it's a fairly complex shape to fit to, so I slathered them with some epoxy thickened with wood flour to fill any gaps.
Sorry I didn't take a pic.
I didn't do an end pour.......I think the blocks would be easier and I like knowing they are supporting the toggle handles.
Ian

: Jim