Originally posted by InitialD
Oh no... I think you're mistaken here. If you had driven the 710 and played around with the adjustable rear roll center, you will notice that with a higher roll center, the rear of the car rotates VERY easily when compared to lower roll center. Very fast in and out of the corners. I don't quite like it but some drivers prefer this. I guess it's just a matter of whether the Tx end is able to control it ! 
Playing around with the rear sway bars will affect on power steering. Playing with the rear roll centers will not affect the on power steering balance.
Anyway, I think I'm confused here. You mentioned earlier that you modded your upper rear arms already with the dremel. So now you say you have not?
I did mod the arms not like you did but i took the dremel with a rough grinding tool and the front of the arms where the curve is i redeced the angle of the corner and took off more than half the thickness of the front are and took a little of the top of the pivot ball area then polished it up with a light sanding tool
I have yet to drive my 710 waiting to get a new power plant as my .12 MS turbo 3 port is still in my 705. so you think i should run as large a spacer as i can get to fit in there? I would help my handeling with out having to increase my rear swaybar tension