This is the phrase that concerned me:
"You must capture and void orders and order authorizations with the Authorization and Capture APIs. You cannot process order authorizations through the PayPal website. The PayPal website only supports processing basic authorizations, not order authorizations."
It appears you have to go outside the system and use hand coded API's to create the authorizations, and I'm wondering if that is just beyond the capabilities of integration into eCart... which from my experience sets up automated transactions (only?) with Paypal...