Hi Dave interesting question yes barrel mirage does have an effect on you elevation when you are sighting through a scope. The best method i have seen was a luever out of a blind with velcro tabs to keep it in place, a great idea i have seen it on lots of top shooters outfits so they must work.
For me personally i don't use anything on the barrel, i know it probably doesn't matter but once a get a rifle shooting the best it can that is how the rifle will stay. All things to do with accuracy come from harmonics so if your rifle is fitted with a mirage band and shoots the lights out with it then shoot it that way all the time.
Also it has been my experience that with the size of the barrels we shoot in the fly that mirage is not a great threat unless you are running your shoots hot and quick.
Les
shooting well is more a mental control of your thoughts than just pulling the trigger........