... I'm just not to sure about my clamps. I have those one hand
> squeeze bar clamps that come with rubber protectors on the clamp faces.
> The problem is the protectors tend to slip off when the clamped faces are
> not exactly parallel. This effectively loosens the clamp and the joint
> ends up with a gap. I've even had the clamps fall off the clamped pieces
> entirely. . . .

When you cut your braces for the hatch covers, save the scrap pieces.

If you cut the curved brace out of a rectangular piece of wood (as opposed to steaming and bending it) then the scrap that you cut off can be used with your clamps to keep the clamp jaws parallel, and the clamping pressure even.

The convex and concave pieces that you cut from your original stock are stacked like a slices of bread in a sandwich, surrounding the layer of plywood (or strip-assembled strip panel) that forms the hatch. Put glue only the piece you want to stick to the hatch, and clamp away. The unglued piece will help spread the clamping pressure over a larger area of the curve than flat clamp jaws ever could, and the pressure will be more even as a result.

If you have been extremely frugal and have very small scrap pieces they may slip around while you tighten the clamps. If this occurs, you can use a brad driven through the scrap and barely into the hatch cover to hold them in place. The hole from the brad can be filled in later if it should be noticeable.

Hope this helps.

Paul G. Jacobson