Thanks for fixing the link. That's another little known thing- an average field (max) produces three harvests of lettuce. I don't have actual data, but based on my experimentations I think a realization of 13-20 harvests is possible; actually there's literature on this as well. How exactly? Just a basic application of the queuing theory. A lettuce needs to sit in the main hole for max 20 days. Before that, within the same 2k sq. ft. that I mentioned, keep it in separate 'incubator'space which will take much less volume.
In the coming weeks I'll add pictures too.