Would someone please confirm this for me.

If I have "shipping calculations" on in my PayPal account, and Zen Cart sends an order, PayPal will add more shipping to the total? Then I may get an error because the two figures do not match?

I have my products also listed on a site that seems to rely on my PayPal account having shipping "on" in order to charge it. A customer purchased some soap yesterday and I had to request the shipping separately plus pay PayPal's 35 cent base transaction fee twice, once on the shipping, once on the soap. Needless to say, I lost money on that transaction and I do not think the person will be a repeat customer. He was none too happy I had to request the shipping and decided to take up the USPS cost of Priority mail with me.

Thank you,