The stock ones used on convertibles, Mach 1's, Bullitts and pretty sure Cobra's as well aren't really subframe connectors so much as they are floorpan stiffeners. In order to be subframe connectors, they would have to be long enough as to actually connect the front and rear subframes. And in order do be effective, they would need to be constructed of thicker steel like aftermarket sfc's are.
The only useful added bracing that was specific to convertibles is the K-member brace. Not sure if it would be worthwhile to stick one on a hardtop car, but they do function well as a skidplate to protect your oil pan if your car's been lowered, haha - mine definitely has a couple scars.
The only useful added bracing that was specific to convertibles is the K-member brace. Not sure if it would be worthwhile to stick one on a hardtop car, but they do function well as a skidplate to protect your oil pan if your car's been lowered, haha - mine definitely has a couple scars.