Theft-proofing a convertible with no steering lock

I had a friend who restored old mustangs at his home and would park them in his side yard for sale when he finished.

After having more than one stolen he got so he would let the air out of one of the tires when parking it outside.

Told me he never had them steal one with a flat tire , and just to keep a full air tank or 12v compressor with you to re inflate the tire.

Then there is always using the club steering wheel lock along with the one that locks the brake pedal.

Or do what I do and not park it anywhere I can't see it , an exception would be the weekly cruise nights where I just take the keys and hope for the best.

Also I have a stated value for it on my insurance , is a little more but makes me feel safer