Okay I updated to version 6.05. And tried to recreate the checkout again. The first time I did it after updating it put several errors in the code, I tried again and it didn't give me errors but things still didn't work like they should so. Figured the best approach is to address each issue as they arise. I've created the files again and replaced the form fields on the checkout page with hidden fields that get populated when the user logs in. This seems to work up to the point where you click the Continue button which loads the Billing and Shipping info correctly. But the Paypal Advanced window doesn't load in the iFrame.