...to steer clear of your neighborhoods!
Yikes.
I've owned a roadster for 25 years and have never had anyone steal anything out of her.
As far as "never parking with the top down" as a theft deterrent, that's crazy. If they want to get in, they just cut your top with a pocket knife and reach inside. Better to just leave the top down and let them take everything they want, but leave you with an intact soft top.
Who leaves valuables in a car anyway?
No car is safe, fixed head coupe or not.
Cheers.