Thanx George and Roger...

OK, here is another question:

Am I allowed to use 4/0 AL (XHHW/USE) to each of the 2 200amp mains according to 310.15(B)(6)?

Seems to be a gray area disputed often. But in reality, with the load diversity of dwellings, I don't think it would ever be a problem...

But also, XHHW AL is good for 180amps and the next size up breaker is 200amp...right?

shortcircuit