I've been a customer for 4 years and have a 510. I sent an email to the ceo address and requested that they activate a 522 if I purchased one. After a few emails they agreed and I have had it working for a few weeks.
Just fyi, my installer put in a legacy quad last year before the DishPro stuff came out. It works great, have 1 lead going to a 510 and two others going to a 522. I can use the 4th lead for another receiver.