Well I got my lower stress bar (Bristol Bar) yesterday and installed last night. Installation was a snap with good instructions. The hardest part was chocking the wheels and jacking the car.
I then took her for a quick spin over my local test road. This is a public road so I wasn't really pushing it but I got in enough spirited cornering to feel a difference. Definitely more planted and precise at the rear wheels, especially over uneven road surfaces. Track days are coming soon so I will know more over the next month.
As an added bonus I noticed an absence of creaking noises from the top while slow cornering through rain gutters and up my sloped driveway that normally cause a little chassis twist.
Thanks to insite for discovering this little gem and Kirk for your product development.