I have a microbiology background in a prior life. Pathogens won't grow at 53°C, although they won't all be killed. So if you held at 53 and then let go back to room temperature where they can start growing again, you have a potential problem. The goal is to make sure that nothing grows while they are held. However, holding at 57 would probably work just as well. (Pasteurization at the link you sent was 57°C). Two servers. I like the idea of ramekins with toast on the side. Another option, that I have seen, might be to serve the eggs family style (in portions of 4), that would hold the heat better than individual portions. The set-up doesn't allow for more than a couple of sets. Seating is family style at long tables. Thanks for the suggestion!