: An easy thing that comes to mind would be to simply epoxy some cross bracing
: on the underside of the hatch before cutting it out. You could do this
: prior to cutting the hatch by marking your hatch cutout. One way to do
: this is to do a partial cut out of the hatch so you know where to postion
: the braces. Small holes drilled at different spots along the cutout line
: would also accomplish the same thing. One caution: make sure that your
: braces are set back enough from the edges to clear the hatch lip.
: Installing the braces before cutting out should prevent any spring back

The stressed deck will also change shape a little when you cut out the hatch, so I would reinforce the edge outside where you cut it before cutting.
JohnK