Sorry for the delayed response, I have been travelling on this week.
@HKTarzan, @thiagoralves- I think that better place for the USB connector would be on top. It is after all debug feature, that is not constantly needed. IMHO front panel should be reserved stuff that is used in normal operation.
@HKTarzan - Hole in the PCB should be 2.2mm - 2.5mm (x6). Four corner holes will need at least 4mm (diameter) circle around the hole that is free from components. Two holes around the bus connector will need at least 5.5mm (diameter) circle that is free from components (and isolated). We will use M2 washer with the the two bolts around the bus. Diameter of the M2 washer is 4.5mm - 5mm depending of the supplier.
If I missed some questions, please poke me.