"Gaucho10 - when you feed does that effectively block the air flow through your ventilated top?"
No it does not for two reasons. First, I feed using a 1/2 gal. jar with its cover perforated only half way across. I can rest the bottle with only 1/2 its cover on the edge of the opening. I can also feed using that same jar by placing the jar on a circular metal bar that I formed out of a plant hanger ((1/4" solid metal bar). This bar fits right over the hole resting along the edges but it keeps the bottle raised approximately 1/4" above the opening so that air continues to flow through the opening and out through the small 1" perforated/screened holes along the side. (Pewff...run on sentence!!!!!!!)
Someone asked before if the bees could reach the perforated jar cover if the jar was resting on a screened covering over the hole. I believe that it was Michael Bush that answered that question in the affirmative.
If you notice my hive, the outside is covered with 1" insulation which I remove in the Spring. That would deffinitely not be the way to go if you have many hives. In m case I only have 5 at present and this is all a game/experiment to me anyway.