Dr. Byte -

Are you saying that once I have my PayPal API Security settings -

Specifically: API Signature -- Username
API Signature -- Password
API Signature -- Signature Code

- that these can be used for multiple Zen Cart stores/shopping carts, and I can still personalize the carts for the different stores they represent?

BUT - We have to specify a URL at PayPal in the IPN Preferences - and we can only specify one URL. That's one store. What happens when payments come from other URLs - from the other stores? Not sure how that works but you are usually good at making these things sensible.

Thanks again, in advance!