I personally don't use warningshots as a Pirate anymore
I did that, but when i did my targets ran or tried to engage me as they didn't understood that - so it pretty much depends on the target you encounter
you could ram him instead works great on train alike
i got another thing... IF there is enough RP and a Pirate drains your shield 70% as you didn't pay fast enough it's not even a RuleViolation i guess, right?