: I do have the spreader sticks, but I still have worries about
: cutting the hatches out before I attach the deck to the hull.

: Charles Robinson

Charles, I wouldn't worry about a mis-fit on the hatch cover from matching the deck to hull later. In addition to using spreader sticks, consider also 'tabbing' the hatch cut-outs, so the hatch lips fits the hatch cover precisely. See photo below, and also Kurt's page on this.
http://mysite.verizon.net/NGC704/newOI/Page_7.htm

Additionally, hatch stiffeners on the underside help reduce warping.

There is a lot of work on the inside of the hatch lip that is difficult if you wait until the deck and hull are joined. The easy access to the underside while they are apart is a joy.

John