I believe there are eight or nine of us who had done the dirty dance several times while it existed. We each have a certificate and souvenir Mexican hat to attest to our acumen with airline tarrifs, and ability to confound Immigration and Customs agents who couldn't understand why anyone would travel 5K out of their way, through three or four airports, all within 24-hours. Or those MX flight crews who after saying "adios" to us at CUN, only a few minutes later were saying "buenos dias" to us as we reboarded and settled into the very same J class seat we had just spent a few hours in. In all this, I believe only two MHD runners were actually pulled over for a secondary immigration interrogation.
Credit for discovering the MHD goes to Ken Haamer and Blonde Bomber, who found a way to fly transcon Canada in the front cabin on a fully flexible ticket, for slightly more than an H-class restricted economy fare ticket: C$1200, or $US800. Base mileage accumulation was about 12K, but many of us completed our trips when AC had a status mile bonus going, yielding another 4K [about a third of the travel mileage was not eligible for the bonus as it was on MX not AC].
I think this winter we should have a Mexican reunion for all MHD runners in either Cancun, Puerto Villarta, or Mexico City itself.