Yep, that's how I did mine. Use your old one for a template. If you can't do that, get ya some treated 1/2" plywood, and a treated 2x4" or 2x6". Rip your lumber into 2x2" material for cleats. Next, measure the width of your exhaust manifolds, and the length from stern just past your water pump pulley. Cut your plywood into those dimensions. (give yourself a little room to play) Attach a cleat UNDER your plywood on the stern side. This will be where your hinge mounts. Now it's time to build your sides. make sure everything you attach to the top goes underneath it. Use your cleat material mounted 1/2" inside your top, and attach your sides to the cleats. Here is mine. It's an exact duplicate of the original right down to 1/8". As you can see, it's not overbuilt in the factory. That's why everything needs to be mounted under the top, and not to the side. Assume people will be sitting on it in choppy waters. Mine has flared sides, and some funky angles. S quare would be much easier than this. Next comes foam, and marine grade vinyl. Might even foam (without vinyl) the inside for noise reduction.
