For the past three years we have put about 10,000 miles/year on our hacks in just that configuration, using a GL1200/Motorvation road rig and a XR1200/Ural Dual Sport for off road.
Short trips (with no extra ballast) to longer trips with camping gear surrounding the canine, no problems.
We'll travel 75-80 on the freeway, but generally do not push the envelope on the twisties.
That said, the canine is not real happy when flying the chair.
Do it, enjoy it, but don't be crazy...
Just because you're not paranoid doesn't mean they aren't out to get you...