I saw some hive top feeders that hold jars, they were made from 7/16" osb. So I made a handful of inner covers with 7/16 osb. I made a pine outer rim. The outer rim has to be a bit thicker, but its basically the same. Not too heavy, but heavy duty. Cut a few jar holes, and the jar lid is almost the same thickness as the osb. So there is no need to thicken it up to hold jars. I used em all last year and my opinion they are good.

Rob