Get it as close as you can, but better to have a little overlap than a gap, in my opinion.

Use some nylong webbing or straps in the area you're having trouble with and it should stay put long enough for you to get it epoxied.

FrankP

Is this an S&G, or a hybrid? When I built my S&G SW17, I also had a heck of a time getting the deck to make w/the hull. I had problems where the hatch sills are, because they stiffened the deck too much for "tweaking". Its normal for the deck to spread noticeably after removing the temporary deck form. ("sprang!"). Try using a putty knife or small screwdriver to lever the pieces into alignment. I did this, but I still had a small overhang in a few spots, which I had to sand down. No one ever noticies but me!

If you are painting the hull, you may want to consider extending the paint about an inch or so onto the deck itself. This is fairly popular, I've seen some nice examples, and it would cover any "adjustment work" at the shear-to-deck joint. There are instructions somewhere on this site, using a compass to draw a line around the entire deck, then round slightly at the bow & stern.

It's a S&G. Thanks for the tips. I'm also thinking of using some packing tape to hold it in the bend.

The foredeck of the Jimmy Skiff also has some bend.  In this case, the deck is ring-nailed and epoxyed to the sheer clamps, and it takes its shape from the rounded top of the forward bulkhead.  When it was time to attack my foredeck, I smeared on the epoxy, and plced a thick manilla rope with 20 lb. of barbell weights tied to each side over the deck.  Then I pounded in the nails.  Next day, I removed the weights, and the deck's been attached ever since.  I did the same thing again for the deck reinforcement strips/splash deflector: five lb. dumbell weight suspended from the ends of the strips like earrings, day for the epoxy to react, on like they grew that way on tree.

If you haven't already installed the hatch lip, I'd recommend not doing this before attaching the deck.  It's much easier to bend the deck first, then attach the hatch lip.

FrankP

I also had a tough time getting the bend in the deck on my Shearwater 14.  I used the clear packaging tape (the wide stuff) between wires and it helped.  The only problem with using tape is that it can pull a few splinters of wood off when you remove it.  I used quite a bit of tape for the final deck-hull mating (by which point the hull has been fiberglassed so no big deal) and did a very thin saturation coat of epoxy on the top of the deck prior to this, so there wasn't a problem with the tape pulling up wood.  A putty knife or drywall spreading tool helps too - slide it between the deck and hull and push the handle up to pry the hull out.  The bevel on the top of the hull joint should help hold it in place once you get it pried out and taped.