I assume this car will be street driven. I will give you the advice that I give anyone who asks.
"I" wont put a rear bar on a car with stock(ish) front travel/suspension unless it has a front bar. I've seen WAY to many cars get a little out of shape and have the action exaggerated by the stiff rear and loose front.
If you go with a rear bar, make sure you have one in the front also.
Watch youtube. Any drag car crash video compilation will show this in action. You will see the car sway a little bit, one rear tire will come off of the ground, the car will act like a tricycle and boom. Done.
Don't misunderstand. I don't blame the bar for the initial looseness, but the ability to correct a car that has stock travel in the front, no front bar, and a stiff rear is a handful, even for an expert driver like me