Think you are talking about the
swagman bike rack...
we got it and
this extension to give it more room between the rv and bikes - between it and the sweep "up" of the bike rack it gave us enough room...
but you are right about the amount of movement !
Putting about 10 bungee cords helped, but still was a lot...
and I even had
these hitch locks to tighten it up...
one thing to make sure of is verify if the company will warranty the rack if behind an rv - the swagman wasn't so I returned it !