Joey,
One benefit to adding a riser is that it will increase the distance between the two vehicles, beneficial when cutting tight turns.
I experimented first without the riser, later with the riser. In a parking lot, I cut the motor home as sharp as it would go and did a donut to see whether there would be any concern of the two vehicles making contact. Without the riser, it was "scary" close. With the riser, it was comfortable.
One more consideration is the motor home when loaded up on a trip. Having a tank full of fuel & fresh water, gear, food, etc. all combined will influence the height of the rear hitch. You won't need to actually load the motor home, but rather consider it will drop 1-1.5" when determining the offset hitch adapter. So if it's a little high on the motor home side, you should be good. If it's a little low on the motor home side, it will be lower yet when on a trip. So I advise to error on the "high" side, assuming your rig is empty when measuring.
Before towing our Liberty, we towed a little Toyota MR2 Spyder. By shear luck, the bar happened to be level. We never had any "bucking" action, so it had me wondering what the heck was gong on with the Liberty. Without the riser, the Spyder was closer to the motor home, but because of it's curved front bumper style, there was a lot of clearance between vehicles to do donuts. That Spyder was a very friendly tow vehicle. It was great on paved surfaces but not so much going through dry river beds...hence the Liberty 4x4.
