Tom Barrett asked about drone escapes.

Tom, Thorne (and some US dealers as well) sells the plastic cones (red) that
are the basis of the Canadian bee escapes.  They work great as one-way drone
escapes.  You will have to make up a board to put them in.

However, you don't really need drone escapes to use the two-queen system you
are describing.  Such two queen systems are commonly used here in the US as
comb honey production colonies.

Here in the US, the hives are run with two queens (as you describe) until
the honey flow commences.  The top hive has an upper entrance (below the
excluder) that is used by drones and some workers, as well.  Usually these
two hives each get quite large just before the honey flow, with each often
consisting of two deep Langstroth boxes, plus a medium!

When the flow starts, the upper set of boxes is taken off and set aside.
All the field bees from this hive will return to the remaining hive, and
find the entrance.  As you know, during any flow the bees to collect the
nectar will principally be those old enough to be field bees at the start of
the flow.  Supers (two or three) need to be added immediately when the top
hive is taken away, and more may be needed in another 7-10 days!

The disadvantage of this two queen system is that the combined hives get too
large before the start of the flow...and if they are not allowed to get very
large they will swarm!  However, if one is willing to put up with such large
hives, they will get a truly astounding amount of honey.

I hope this helps.

Lloyd
Lloyd Spear, Owner, Ross Rounds, Inc.  The finest in comb honey production.
www.rossrounds.com