None of us here will be anywhere near as good as a thorough look at the instructions for the unit you're considering. In all likelihood, it will involve quite a bit of wiring work and will turn out to be one of the many, many cars permanently electrically chingered-up by the installation of an alarm that has its grubby little tentacles in every branch of the vehicle's original electrical system. Malfunctions, won't-works and bizarre sets of seemingly unrelated symptoms are extremely common with aftermarket alarms, even with "professional" installation (usually done by the Taco Bell rejects at Beast Buy or Cartoys or Circuit Shitty or the like).
And then someone throws a brick through your windshield because your stupid friggin' alarm won't quit going off at 3 in the morning, and how does that help you?
You own a convertible. Convertibles are less secure than closed cars. An alarm will not significantly change that. Your convertible has a trunk. Use it.
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