I think he can get the record down to low 42s if not break into the 41s if he's dedicated to running it for the rest of his life.
If he's not then just sub 43.. maybe 42.5-42.75 range before he tries to go back for 100m/200m.
He has a HUGE speed reserve where running a 10s 100m for him is easy compared to most of the current and past 400m runners. When you make very fast times really easy, your speed endurance increases immensely when you tone down your speed even just a little bit.
Current record is 43.18 for reference.
Last edited by Steven Low; 02-10-2010 at 07:09 AM.