Sorry but I'll take issue with the statement that Paypal standard doesn't have a sandbox. I think that is misleading. The sandbox does a very nice job of testing PayPal Standard apps. Yes there is a manual process that you have to go through to test IPN but you can test everything else from passing the data to PayPal, making the payment, returning back to your website, and capturing the PDT information that PayPal sends back.
And imo any application using PayPal Standard should be using both PDT and IPN.
I realize that you guys don't like PayPal Standard and I can understand why, but if someone says PayPal Standard is what they are going to use, then really you should do everything to support it, especially considering PayPal Standard is a choice inside of the Checkout Wizard.
I asked a simple question, never got an answer, and figured it out myself. It was so simple I suppose I should have never needed to ask.