Welcome back Fongo!
I did two of them. I love it, even though I did not succeed on either one. Ours were way too hard. I am looking for one that doesn't involve way too far out there thinking. For instance, in my circle of friends and family we did these with a top attorney from a well known large worldwide corporation, a programmer, a realtor, an accountant, a carpenter and me, who writes strategy guides and figures out game puzzles on my own before games are released. I would have to say we have a fairly intelligent group. We could not do either one except for a few steps.
That is cool that you are running one! Too bad you aren't near CHicago!