Yes. But first I have to ask whether you have full length subframe connectors (MMs for example) welded under your car? They make much more difference than the STB.
Factory subs are a joke. If you want to stiffen your car (and you should) then buy yourself some MM full length subframe connectors. Have the car lifted with the weight on the wheels and have them welded in.
Didn't the convertibles come with a strut tower brace from the factory? When I bought mine, it has one. Car is all stock expect for what I have done to it?