I read somewhere, sorry I don't recall, that when this 4.9 mm foundatin is used, drone foundation should be used as well to encourage the bees to lay drone cells there for the purpose of catching mites. The mite, it seems, prefer the drones. The drone foundation is then frozen overnight to kill the mites and left to the bees to clean out.
I just wondered what your thoughts were on this. If this is the case, wouldn't this characteristic just be quickly bred out of the mites?