The get the size and shape of my hatch just right, I took my two side pieces, clamped them to the walls with 1/8 inch spacers, and worked them with a planer and belt sander to match the walls perfectly.
Then, i measured for each cross piece separately, cut them, and did a dry fit to make sure my fit was right.
Then, I took the hatch pieces, assembled them, and put the hatch back in place with clamps and spacers, and let the glue dry.
I also skinned the hatch on the TD.
CD