Re: Is exceeding hitch capacity by just a teeny bit ok?
There is a data plate somewhere inside of your RV, usually in a cabinet, mounted on the door that will have all of the weight ratings of the unit. It should have a figure for max. towing weight, for gross combined weight (GCWR) and for the gross weight (GVWR) as well as the ratings for each axle. Those are the weights to concern yourself with first. If you do not actually weigh the motorhome, then assume that you are traveling at the gross weight, although it would be wise to weigh it and to get the weight on each axle as well, just to know that you are not already over your rated weight.
If you tell us what chassis you have, we could determine the ratings for it in terms of maximums, but you will still need to know what Winnebago/Itasca did to the chassis when they built the RV. The data on the plate of sticker will tell you that but actual weights are also very important.