KB7OUR

I agree a shallow formed metal box with a top flange bent at 90 deg from the sides to form a lip to rest on would be ideal. I doubt you would even have to bolt it down as it would likely fit nice and snug in the cutout. Maybe some construction glue around the lip and two drain holes in the bottom to match the ones already cut and screened. This would be a very sturdy setup and all you would have to do is find a shop to cut a single piece of metal (maybe heavy aluminum?) and bend it to shape. Snip the top 4 corners so you could bend them down to form a lip and drill two holes in the bottom. I'll take one!

Wade