Is this possible?

I want to have a flat rate shipping cost for items 1 or 2 lbs that will fit in an envelope, but only if that one product is ordered. However, if a small item is bought in conjunction with a larger item this option would not be shown.

Also, I was curious to see if someone had a good set up for the talbe rate shipping costs, and could maybe show me how to set up different zones to calculate different shipping options. Right now I am using UPS and USPS which I don't think are bad options but I feel that some customers are turned off by the prices.

Thank you!