The answer is above. I think iwire's post is the answer you were actually seeking.

Think about what is connected to it, and forget about the number of breakers for a minute. If you've got 21 amps on each leg, you will have 21 amps on each leg, period.

Now, split it up however you'd like.
4-15 amp 1 polebreakers with 10.5 amps on each of them.
42-20 amp breakers with 1 amp on each of them.

The panel still sees a load of 21 amps per leg.

Get it? It's the LOAD, not the # of breakers.

[This message has been edited by electure (edited 02-19-2005).]