With too large of a roll bar, if one wheels is 'upset' mid corner then the same energy will be trasferred to the other wheel, thus causing the whole front or rear-end to being upset.
A Fat one is ok to have on a car that only ever sees a nice flat race track, but on the street you have to find a good medium.
I'd say one similar in size to what the XRs ran at the time would be a safe bet.:beerchuge
1993 ED XR6 M5 (1 of 329)
Turbo on the way!!
1993 EBII Fairmont (Now wrecking, PM if you want any parts)
1988 Nissan R31 Skyline