Here's an idea I'd like to try and I wonder if anyone else has done it and how it worked. First, some background: I have used formic acid for mite control for over ten years starting with homemade Miteaway II pads, then using perforated VHS cases to hold the ten test soaked in 65% formic and most recently mite wipes (meat tray soaker pads). In all cases the bees propolize the perforations or, in the case of the soaker pads, make propolis dams around the pads. With all delivery systems I use a reversible inner cover with a 1 1/2 deep rim on one side to make a cavity to help contain and disperse the vapour. My idea: how about placing the formic pads on top of a propolis mat with the inner cover cavity over that? The bees natural tendency is to propolize to contain the vapours; the propolis mat is replaceable when plugged, maybe one could treat for varroa and collect propolis at the same time. Thoughts?