One of the NVAV members has built a beautiful RV-7a and his call sign is PH-OBO. Since he is a Hobo-player, it looked to me that the call sign could not be a coincidence. After some research (and an email to the department of ILenT), I found you can reserve a registration (call-sign) if the registration is not used and wasn’t used the last 30 years.
You can browse the Dutch Civil Aircraft Register database to look for available call-signs. Here is my list of potential call-signs that were available.
I really had a hard time choosing between the top three. However if you factor in pronunciation and character esthetics’s, PH-MNX is the winner.
So that one is now reserved for one year and needs to be extended yearly until it flies.