I have been shopping for sheet metal with which to cover my TBH's. Cheapest sheet metal I can find is around $20 per 8 foot sheet, two covers.
Found some two-foot aluminum roll flashing metal today for $1.29 per foot, $5 to cover a hive. Made a telescoping top with one ten-foot 1x4 and a piece of plywood. Very nice drop-over cover. It will rest on two integral runners to keep it an inch off the top bars, at the same time holding the top bars down until they are propolized properly.
This covers the Hardison design. Will work on the Crowder top tomorrow.