So I was under the car doing my TSW spring install, thinking about how I wanted to set my RSB up when the job was done... And then it occurred to me I have no idea which way is which in terms of stiffening / loosening the bar! It's a typical 3-position bar, and I got it from the PO set in the middle - So I never thought to play with it untill now.

 

Further away from the bar is softer. The hole closest to the bar is stiffest.

 

I would see how you like the handling of your mini at current rsb settings with the new springs before you change anything up. The TSW springs are linear, which is great because they provide great feedback. I left my bar (19mm 3 position unit) in the middle because I felt like I didn't need to tighten it up any after my TSW springs were installed. Very neutral turn-in, especially when paired with a set of really good street tires (I have Hankook Ventus RS-2, but any equivalent would work as well). I moved it to thr stiffeer setting just once, and it tended to oversteer the car a bit.

Again, its different with a user by user basis.

 

^ Neutral with a 19mm bar in the middle? I'd say my car is neutral with the 25.4mm hollow bar in the middle and still has slight understeer with it in the soft setting.

Certainly different drivers like different styles. I've got TSW springs like you. I've also got camber plates up front (more camber) and arms in the rear (less camber), zeroed toe, and 3mm spacer in front and none in the rear. Certainly a twitchy setup, but I'd still say it understeers, I can certainly throw the back end out BIG TIME if I want to...but its understeer at the limit for sure.