4 down behind a motorhome is a very common and stable usage for Jeeps. I would imagine that you would use the same tow bar system (from a hitch mounted on the 5th wheel) for this application? Should be as stable as behind the motorhome with the 5th wheel. My only wonder would be the surge braking and, of course, triple-tow. Never did that with a 5th wheel, but have seen plenty do it.
Jeep might be pretty heavy behind the 5th wheel also and you'd have to have a strong hitch to the frame. Also not sure how much your loaded weight would be on the Redwood, but you might be over GCWR totals when adding in the Jeep.