Russell, I have a few ideas which may or may not help.  The first:  I
have found that my bees (Italians from Weaver, their All-American)
prefer to draw out almost anything but duragilt.  If I place crimp wire
foundation and mix it with duragilt, the bees always seem to start on
the non-plastic base foundation first.  Maybe your hives preferred
starting on the non-duragilt foundation before being forced to work the
duragilt?  I have read that bees like to have a certain percentage of
the population in the hive to be drones.  It might be that by limiting
drone population in a hive that we are "prompting" the bees to produce
drones.  The last idea I have is that I believe that the AHB has not
yet reached Weaver (Navasota, TX).  Weaver produces a brochure that they
send along with an order that covers this topic.  I would suggest contac
ting them.  I think that the gist of the article is that with drone
saturation they feel that they can achieve over 95% certainty that a
cross will be European.  It is based on reseach conducted in Mexico that
was published recently in ABJ.  Hope this helps.  By the way, my wife
works for IITRI here in Chicago.  I didn't realize that IITRI had office
s out in Maryland.