MarketPress: Table Rates

Is there a way to not lose all of the date entered into the table rates section when you try a a different shipping method?

Also not sure if there is a way to have a flat rate shipping for certain items and the table rate or USPS for others.

For example the majority of items I will be able to ship via USPS, a couple of items I will have available in the future will have to be shipped via truck and have a flat rate price.

Thanks in Advance!