And as to a 4:30 sprinter mile, I believe there are only 3 guys who contribute to this board who were sub-10.5, and of those 3, I am the only one who has recorded a mile time.
That mile time was after lots of "distance" training, and 20 years after I was seriously training for, and competitive in, sprints. And I only ever so slightly broke 5 minutes. And it nearly killed me.
Try this: find a short sprinter on your team, and ask them if they are willing to run a timed mile.
First off, there is no way they will agree.
Second, if they agree, let us know what their time is.
Third, record the distance at which they hit the wall.
Fourth, if possible, get a video.
Decent 100/200 guys might go around 6:00. Decent 200/400 guys might go around 5:00. None of them will go 4:30, unless they relatively aren't that great at the sprint, in which case they should really be a middle-distance runner who got put in the sprints because your team is relatively weak at the shorter distances.
A big thing about even middle distance is that pacing is critical--and of this concept, over the longer time period, sprinters are clueless. Also, a proper warmup is critical for aerobic events--and sprinters are clueless of this, also (i.e. an aerobically-beneficial warmup). These things apply even when the "sprinter" is a thin and wiry 400m guy.
The mile must be trained to be run in 4:30--not just jogged every now and then. It must be run at speed, to understand how the body responds, and to be able to optimize performance and stay within the envelope without hitting the wall.
Sprinters know nothing of these concepts. The running, the training, everything is different (of course).
My final thought is that there is no way you will be able to convince a short sprinter to run a timed mile, unless you offer him some serious incentive.