For all the people with large number of chips, the most feasible option would be a double density board with 20 Chips at about 100eur.
Even larger boards would pose problems that I don't want to face, doing such a time-constrained project.
I don't want to burden you burnin since i know you have a lot of work to do, but please have in mind posting some pros and cons with the double density boards.(not now, but when you are ready to take orders)