Murray, No, I do not use reversible bottoms. I monkey my own [an oxymoron: how many Ph.D's does it take to make a bottom board?] bottom boards, and I do not carpenter to create a "Winter" bottom, which many would argue as "obsolete," too. (I am just too lazy to switch even if I had them.) Since I offer a little crack between the outercover and the inner cover, I thought wire-mesh, mouse-guards on summer-entrance would provide more vent in the winter. I am sorry for changing the topic here, but how serious is the mouse damage in the south? Yoon