So I think you answered my first question with, Yes it can be made do work.
Sure same version SW, but should I upgrade the old units or should i downgrade the new units? On the back of the new units there is a red text printed: ENCRYPTION & PPM but this is not printed on the older ones.
That is not in the wiki.
I realise this is maybe not the place for this discussion and hope my support ticket will be answered in due time.