Sometimes they have a sign up for a bunch of different already filled IMs after other tris. For instance, at Gulf Coast Triathlon in Panama City, which is a half IM distance in the spring, after the race (can't remember if it's the afternoon of the race or the afternoon the day after) some woman from IM comes, and people line up very very early to get about 40 slots for different IMs. That's how BF has gotten into IMFL after it was closed- but they also had Wisconsin and other ones available. They must do that in other places, too.
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"...I'm like the cycling version of the guy in Flowers for Algernon." Mike Magnuson