Thanks,
Couldn't someone strip that pool specific portion of the hash for non-winning work and submit it to a different pool then? (or does it change with each hash also?)
Changing a single bit in the work template the pool gave you will completely change the result of hashing in a non-deterministic way. So if you change anything about the work, you have to re-hash it. There is no way to squeeze out "extra" shares from the same amount of work by submitting to multiple pools.