Sorry, got to disagree here. 1mm more on the rear bar isn't going to do much of anything. With the 25.5 H-Comp on the softest setting, the car still understeers.

As to the JCW suspension, see this

On difficult, tight runs the MINI with JCW sports suspension can be steered even better into bends. The slightest of steering-wheel movements are enough to maintain the MINI on course. The inner front wheel maintains contact with the road surface, thus allowing the MINI to accelerate faster out of the bend. … I wholeheartedly recommend the JCW sports suspension to adventurous drivers, who like nothing better than taking to country roads and winding mountain routes.
http://motoringfile.com/2004/11/12/j...sion_in_detail

Addin the JCW suspension made the car MUCH easier on my bad back than stock. Significantly enough to be felt.

 

I thought the stock bar was 16mm? Most report that figure. Anyway, there's a lot more to the dynamic than just the thinkness of the bar. My goal is less understeer, and I'll probably go with H&R's 19mm 2-way adjustable (+3mm). Here again, I'm just trying to enhance the package, not change it radically. My plan is for no fuss. No suspension settings to mess with on the Koni FSDs and no lubrication required on the H&R bar ("Ever"). I'll definitely set to softest setting and may change if the understeer is still more than I want.

 

Hmm, I thought it was 17 but not sure.

19 and 22 are standard choice. Some ppl are fine with 19. Most go with 22. In the end, its all a personal choice.

The H-comp is effective 22. There is still understeer. Oversteer dont both me .... we are used to it, Just got to know what to do when the rear end comes around

 

The internet is a great source, and an inconsistent one too. I believe the stock MCS rear bar is 17mm as you stated; therefore my intended affect was to go +2mm...which equates to the 19mm bar. If I was looking to make the suspension more toward race, I would go with the bigger bar. But I bought the car to have fun in while commuting, so I'll opt to keep it somewhat tame.