You might want to consider escrow via John K or other senior board members.
Thanks for the suggestion. At this time I'm not interested in using escrow because I have listed the miners at prices at which I would be happy with immediate payment. If these do not sell prior to shipping, I will either keep them for my own mining or re-list them when I have them in hand at a significantly higher price. When I have them in hand, I would be happy to offer escrow on the condition of delivery at that time.