In another thread you mentioned sub 14 5ks, but nobody on KU has run sub 14 this year (I've been keeping tabs on nat'l lists). Plus, if you ran sub 14 5ks (plural), you wouldn't be deferring med school, you would be trying to land a sponsor after your final season and then hit the circuit.
Do you have eligibility in cross or track? Either way, IMO, you will have enough time as a distance runner to take a normal MPH hours with a cross or track schedule... unless its both seasons? My buddies have done it with one season of eligibility and a somewhat rigorous masters program
EDIT: saw you want to slack off before med school. I feel you there, with the demands of year in and year out cross/track schedule plus injuries, etc. Seems like a waste of a masters though!