Note that Authorize/paypal (and google?) have a limit on how long you can wait to refund (~90 days), and LIKEWISE, paypal (and google?) have a limit on how long you can wait before filing a claim (45 days iirc). Guess when you should ship packages after capturing? -Well- before 45 days.
AND WHILE IM AT IT...While customer literacy is always a bit questionable, if you're finding a lot of confusion about your shipping policies - you should probably change them! YES even if you think you are right. For example, we used to (like everyone else) say that USPS packages were not insured. Guess what? They'll chargeback anyways. So now all packages are insured at a very reasonable rate. We get no complaints about the extra $ - but we DID get complaints when packages were lost.