That's a good question. I don't know the answer to that one.
However, if you have the extra space afforded by the blower spacers, insulation under the blower complex (unless you have cool and/or refrigerated air blowing through under the blower) can keep a little more heat from radiating between the valley and the supercharger.
An aluminum foil envelope with a layer of fiberglass insulation stuffed in it, slid under the supercharger, may do something, too.
I was surprised to read that the blower insulation did ANYTHING, honestly, but people's results have been real, to my surprise.