Good points. Personally I've noted a bigger spark when disconnecting the negative first but I'll believe you regarding the siren.

I have had two camaros in storage for a decade on cheap harbor freight float chargers. I've replaced both car batteries in that time period. No other electrical issues. I don't actually recommend those float chargers but they are what I started with and they have served their purpose pretty well so far. Once the battery dies the float charger draws excessive current and melts. My crossfire won't be in proximity of an outlet so I will probably pull the battery for the next 5 months or so. I do actually agree that leaving the system connected electrically is a safer way to fly because of my experience with other cars.