>>Nobody has mentioned the effect of an open mesh floor to a problem of the
Small Hive beetle.  It seems that the Small Hive Beetle larvae would be
able to reach the ground more readily - but perhaps would not find a home
in a well lit/ventilated hive.
... Any thoughts/observations/experiences?

Would it be fair to theorize then that unenclosed mesh wire floors are
acceptable for use in areas of the US where the small hive beetle has not yet
arrived?
Of course, like varroa, some day the small hive beetle may be prevalent
throughout the US, thus rendering bees treated with this technique too
vulnerable. Don't you really get the best of both worlds with wire mesh
inserts placed over standard bottom boards -- the mites can't crawl back up
to the bees, and you can treat for the small hive beetle underneath the mesh
insert. The major drawbacks are:
1) You don't get the ventilation benefits of the open underside.
2) Some methods of feeding and medicating may not lend themselves well to
colonies with wire mesh inserts over a standard bottom board -- such as the
oft-recommended treatment of applying Terramycin mixed with powered sugar to
the tops of frames in the spring or fall. All the resulting residue beneath
the mesh insert may render this treatment too unhygenic.
3) The beekeeper will have a little more cleaning work to do at
spring-cleaning time due to the build up of debris beneath the wire mesh
insert.

John