I don't know of any plans. You could buy one from David Eyre (hence D.E.) of www.beeworks.com
and use it for a pattern. Or come here and I'll sell you one cheap.
They are nice hives and I have four of them (plus odds and ends) but I need standard equipment.
The Winter/Summer adjustment is that you flip the nex to the top box (the vent box below the lid) over and the lid covers the vents on the lower box for winter. You flip it back and they are exposed for summer. The is a set of vents on the top cover that are open all year around.
It is the appropriate amount of ventilation with the solid bottom board that comes with it. But I find a SBB with a top entrance seems to work fine for me. I close off the botom entrance entirely and prop the top cover up with Shingle shims. Either prop the inner cover up or put a migratory cover on with shims to hold it.http://www.bushfarms.com/images/MigratoryTopEntrance2.JPGhttp://www.bushfarms.com/images/MigratoryTopEntrance1.JPG