Racing Beat, OTOH, recommends against changing the rear bar...
If you want to play (legally) in stock classes, then changing the rear bar is a no-no... The key comes down to whether the car handles more like you want it with the bigger bar.
I know that I could have made great use of a big honking front bar in Oklahoma last Sunday, but I'm happy with the car (apart from body roll) on the surfaces here...
I guess all you can do is try it. Bring jack stands and tools to the next available test & tune you can find, and you can do a before & after comparison in track conditions.