In Don's defense, can you imagine how much his phone would ring if he had a direct number? I really can't blame him there, because every Tom, Dick, and Harry would be calling him nonstop. Fortunately, he has dealers like Olee, Doug, Rip, and Bob that are pretty knowledgable about his products.
I've wanted to talk to him personally several times myself about a few things, but I know that he can't operate that way right now. Your best bet is to try him through the DTR, but bear in mind that he gets hundreds of PMs on there every few days so obviously he can't take the time to answer all of them.
Give Olee or Doug a call first and see if one of them can't help you. Or ask a specific question here on the TDR. You'll get your best answers from people that have used the specific injector.