Testing the PayPal Shop addon in sandbox mode

I've noticed that in it's current state it's impossible to test the PayPal Shop app in sandbox mode because the PayPal URL is hardcoded into the product form template and IPN callback script.

It would be helpful if there was a setting to toggle sandbox mode on/off that puts the correct URL in both files, and perhaps marks orders as live or test. As things stand I have to hack into a few places in order to test my store works correctly before going live.