Take the tow dolly and hook it to the RV with the chains crossed under, then move the dolly to one side still hooked, to the maximum turning point and look at the chain's length, it should be a couple of links longer, and when straight it should not touch the ground.
The reason for crossing the chains is so that in the event that the unit is unhitched the chains will pull and also cradle the trailler otherwise the unit will fall to the pavement and being pulled all hell will brake loose behind the RV.
navegator