I "upgraded" to windows 7 and the new Behringer win7 drivers gave me issues beyond 3 units.
So I went straight MIDI but managed to get 7 units going using only 4 physical midi ports and no USB or behringer's driver.
Here is the recipe: First set both the bcr2000 and bcf2000 to mode S3
and give one an ID of 1 and the other an ID of 2
Now you may set the bcf2000 to McSo emulation if desired.
Now to cable up:
Midi out from a midi interface goes to BCF#1 (midi in)
The BCF#2 OUT port-A goes to the BCR#2 (midi in)
The BCR#1 OUT port-A goes back to the midi interface (midi in)
You could do this with two bcr2000s as well or two bcf2000s too. But not in McSo mode
With the pair only using 1 midi port. It may even be able to cascade more.
I will try and report back.