Think about this
Let's look at this 2.8-3.2 thing mathematically.
For someone running a 6:00 mile, they run .2 miles in 1:12. (360 seconds per mile/5=72 seconds per 1/5th mile).
For someone running a 7:00 mile, they run .2 miles in 1:24. (420 seconds per mile/5=84 seconds per 1/5th mile).
For someone running an 8:00 mile, they run .2 miles in 1:36. (480 seconds per mile/5=96 seconds per 1/5th mile).
So, even Mr. 300 PFT if unaffected by changes in weather, eating and sleeping habits, if he runs his usual 6:00 pace, will notice his time plummet to 19:12 for a 3.2 mile course. Twenty-four minute man will take 25:36.
Going the other way (2.8 miles), super stud would increase to 16:48 and super slug would shoot to 22:24.
Feel free to check my math and fire off ideas...