Some folks have towed all over the world with that kind of config and no issues. Biggest risk is if you are in an emerg braking situation, will it cause a wreck?
(and what turns INTO an emerg brake situation based on the combined weight now...)
My experience with it was awful.. "had" to take a turn a bit faster than desired due to stupid bicyclist on the road... (will try to stay off soapbox)
Short story is...braked hard...then made the turn at say what would be a normal speed non-towing, YJ pushed back end of ZJ around, heading for jacknife. I gassed the ZJ hard to yank the YJ back in place and avoid wrecking myself.
Never flat towed since....continuing on with story, I bought a tow dolly and had ZERO issues, logging 5,000 miles with it. (ZJ pulling YJ)
THEN...watched a buddy wreck his Waggy, towing his XJ using that same tow dolly. XJ swayed and whammy.
So...diff setups seem to work for diff rigs... Since you have an excursion...save up $800-1500 and buy a nice trailer, you will use it all the time once you have one. (or $4-600 for a dolly if you want to try it)
Personally, I now have the excursion, towing a 18' trailer with the YJ on it...
Sam