Sn95 irs

Hi, I was wondering if anyone has experience on dirt with with an SN95 cobra model IRS? I know typically IRS handles better but is it worth the extra weight of the SN59 compared to a fox?
Alternatively, per my track rules I would be allowed to run the cobra IRS in a fox if I wanted to do that. The question being would it be worth the trouble and the cost of finding one? It seems to be a fairly easy swap into a fox. My track rules are: all parts must be stock for make and model but we are allowed to cross model years making it legal for me to either run the cobra IRS in a fox or, a fox 2300 in a cobra.

Has anyone done this or thought about doing it? my main interest is my track can be very rough and without a panhard bar I get too much lateral movement of the rear. poly bushings help that some but with poly bushings I tear the upper control arm mounts off the body. welding helps but then the mounts themselves tear.