The thing is.... To really do it right, you need to increase the size of the front sway bar also.
Two rules... Increase rear bar size and you get oversteer. Increase front bar and you get more understeer.
As the car sits, with a stock front bar, you will have some understeer. Fairly reasonable... Cars back then were designed with some understeer as a safety thing.
Add a rear bar and you can introduce some oversteer... that is the rear wanting to swap ends with the front.... That's not real safe.
Ideally, you want the car neutral. No understeer or oversteer. That's a race car setup. In the real world though, you want some understeer, although you can reduce the amount that the car has to begin with.
There's a ton of other factors... springs and tire size for example.. that come into play, but that's a couple handing basics.
As others have said.. it depends on how you are using it.