We are trying to offer free shipping to customers in the lower 48 states FOR SPECIFIC PRODUCTS only.

How exactly do we go about this?

It seems to work fine for the lower 48 folks, but when we tried an Australian address is seemed to also present free shipping.

These are my options on the free shipper:
FREE SHIPPING

Enable Free Shipping
True

Free Shipping Cost
0.00

Handling Fee
0

Tax Class
--none--

Shipping Zone
48 Lower States

Sort Order
9