Hmm. Me thinks that 8 Marks would be a better target.

Firstly, that allows 1 Mark to earn money and to get hassled by security every time he flies. (Which would happen even more since he admitted cutting his finger with a certain implement, but I think they're maxing him out already).
And since we'd then have 7 Marks, we'd somehow need to keep tabs on which Mark we would be talking to/about. The minimum amount of storage that could do that is 3 bits. So we might as well add another Mark to gain the most efficiency from those bits.