Chassis Mounted Rear Sway Bar?

[alocker]

Any reason NOT to run one vs control arm mounted bar?

I am looking at the Hotchkis rear bar or the ridetech Musclebar for my 68 Impala. This car wont be raced or even driven hard, its just that the rear body roll is so bad its uncomfortable (currently no rear bar). I can very cheaply add the control arm mounted bar but the chassis mounted ones look so much more effective.