I raced IMUSA in 2000. I think Gordo's tips are spot-on.
Your 7-mile stair-stepped workouts will be quite adequate.
Just a slight point of disagreement about workouts...I don't think you should train with your RPM below 70...Even when working on muscular strength...The lone exception would be Muscle Tension Intervals where you could drop a bit, but that's a different discussion. Keep your RPMs high and work on spinning up the hills so you have fresh legs for the run...That's what I did and I managed to negative split the run;-)...Which simply means I left too much out on the course...
Honestly, here are a few personalized thoughts:
1. More people blow themselves up on the Ski Jump Hill at mile 60-ish than do the final hill (where they are already suffering from going to hard at mile 60...Keep your head about you early in each lap).
2. Don't forget to focus on proper nutrition in the final 11 miles of each lap...Many people get caught up in the climbing and forget their eating pattern...much to their demise later in the day.
3. Don't forget a few running hills. The 12 and 24 mile hill can be rough...There is the "Bottom of the Hill" Grill which has burgers/brats cooking while you have to trudge up a pretty steep hill into town...With all the pretty people (don't want to be sexist here), you'd prefer not to walk this portion.
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