Tim,

I live in central Florida about (15) miles north of Orlando.  I have
installed wire mesh bottoms all of my hives.  I have installed them on top of
the bottom board.  I have not noticed a reduction in bees staying outside
during the hot weather.

I find the major advantage of the mesh screen bottoms to be IPM.  SHB, larva
(wax and shb) will fall through the screen onto the plastic coated cardboard
that I slide in from the back.  Periodically, I add a sticky board to monitor
for mites, shb, wax moth and other pests.
Richard