RCP3? I have RC3! Anyway, yep good point. I can't remember if I have seen directions to paste into RC3, but I have seen
'How to get PayPal Api username, password and signature information'
'Copy and paste the API username, password, and signature into your shopping cart's configuration or administration screen.'
Paypal messages have been 'issues' setting up my Sandbox Test Accounts, but seems ok now.
I'm still working on it, so hopefully just entering the email address will be fine in the future.