your speed guys, like a Kerron Clement or Bennie Brazel, would probably run closer to 20.5. more strength runners, like say James Carter, might not be able to break 21.
I agree with PZale. If you train for a 400, you won't have the same start you would in a 200m race, and plus, your mucles probably aren't used to the all out sprint of a 200 compared to a 400.
your speed guys, like a Kerron Clement or Bennie Brazel, would probably run closer to 20.5. more strength runners, like say James Carter, might not be able to break 21.
Benny only ran one open race other than a 400H his entire career at LSU but I would actually guestimate his 200m time to be closer to 21s than 20.5.
I read an interview with Bershawn Jackson not much more than a week or two ago. I can't find the link now, unfortunately, but he claimed to have ~20.4 speed over 200, and ~44.6 - 44.9 speed over a flat 400. Judging from the responses above, he may be an unusually fast one.
The fastest 110H guys I'm aware of are Allen Johnson and Renaldo Nehemiah. I believe both ran sub 20.50 and raced in a couple bigger meets. I'm sure Trammell could run a blazing 200m but I don't remember seeing any 200m results for him.