I have most of my brood in plasticell now for the second year and I'd say it's about 5-10% drones, mostly at the edges of the brood frames.  They seem to be forcing enough cells to drone size to accomodate their needs. 
 
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From:   (Thomas) (Cornick)[SMTP:[log in to unmask]]
Sent:   Friday, July 11, 1997 11:05 AM
To:     [log in to unmask]
Subject:        Re: No drones
 
In a message dated 97-07-11 13:11:13 EDT, you write:
 
<<
 Ever since changing over to plastic foundation and lack of feral hives in
 the vicinity, I have noticed less drones flying in and out of my hives. The
 bees don't appear to make drone cells on plastic foundation.
  >>
   Not seen here  I think once the bees fully draw the foundation out and run
 into the edges they will make drone comb- also once you extract some they
will do the same where the comb gets a little beat up or has blowouts.