I recently visited multiple breeders in the pacific northwest. I had my breeds narrowed to DDB, BMs, CCs, and Boerboels. My primary concern was finding the right breeder whose dogs had the temperament I was looking for. In this quest, I spoke with Teri Herrera of Bandera Boerboels multiple times. I was excited about how willing she was to share her knowledge about the boerboel. I made the trip from Portland to Redmond to visit her facility and I was blown away. She truly is the real deal, everything I was looking for in a breeder. Her facility is state of the art. Her dogs are fantastic, very well socialized, and absolutely stunning (in both looks and temperament). Shortly after visiting her farm I put a deposit down for her upcoming liter between Morgan and Xilo 2. I cannot begin to describe how special a dog Morgan is. I have a feeling this litter will be very outstanding (I was the last accepted deposit on the litter so hopefully I don't bumped to the next one, although this remains a possibility).
For what its worth I also contacted David Harris. Like you, I was never able to get in touch with him. I have tried calling him and emailing him with no success. There is a backyard breeder of Boerboels near Portland (CK Boerboels) who claims to get his breeding stock from David Harris. I also visited his facility and was very unimpressed (although this guy seemed to be a nice person). One of the reasons I contacted David was to see a) if he is truly providing breeding stock to this breeder b) if he knows the operation his breeding stock is going to, and c) also inquire about his breeding program. I would not really consider purchasing from a facility/person I cannot meet anyway but, especially in this case, if I cannot get ahold of the person than a remote transaction would be out of the question for me.
Anyway, I cannot recommend Teri enough. Although I do not have a dog from her yet she is truly one of the excellent breeders (not just an excellent boerboel breeder, but an excellent breeder period). All of her dogs are OFA tested and Penn Hip tested. She has a veterinary behavioralist evaluate the temperament of her puppies before she sends them home. She does charge a little bit more, but because of everything that she does I concluded this was worth it.