Hi Thorsten, 
  
yes, I can confirm. 
  
but  I have to say that two device works OK also with only the MIDIbox.vid selected , leaving both J8 closed and other jumpers untouched ( closed ) 
  
I changed the name in the .inf file writing: 
  
WDM.MIDI_1.szPname="GM5 porta 1" 
WDM.MIDI_2.szPname="GM5 porta 2" 
WDM.MIDI_3.szPname="GM5 porta 3" 
WDM.MIDI_4.szPname="GM5 porta 4" 
WDM.MIDI_5.szPname="GM5 porta 5" 
  
So for the first interface I have ( in MIOSStudio for example and in othe programs too ) : 
GM5 porta 1 
GM5 porta 2 
GM5 porta 3 
GM5 porta 4 
GM5 porta 5 
  
and for the second i have: 
  
GM5 porta 1 - 2 
GM5 porta 2 - 2 
GM5 porta 3 - 2 
GM5 porta 4 - 2 
GM5 porta 5 - 2 
  
The " problems " start with 3 or 4 GM5x5x5 
  
The system dont recognize the third at bootstrap, I have to unplug and re-plug the USB cable to make the system see it 
The fourth doesnt exist anyway. 
And this with various configurations tested (it seems to me I am following the indication in the GM5 page very correctly but it is possible that I am making something wrong ) 
  
Best regards 
Antonio