I just read through all 7 pages of this thread and it brought back memories of FSB/RSB + urethane bushings discussions on the Acura forums years ago. I installed a RSB and urethane bushings on my TSX which wickedly improved the cornering on a stock suspension. One day, I noticed the cornering was much squishier and floaty coming out of a turn I'd rip daily. Upon inspection, my entire rear subframe had cracked. Ultimately, I think it had something to do with the increased stiffness of the RSB and bushings coupled with the much-harder driving I was now subjecting the car to. I had the subframe replaced and re-welded but the car was never the same and I got rid of it shortly after.