I had a friend who was all proud of his 3 or 4 bike rack that mounted to the rear bumper until they left for home on that trip. I got a text from his wife saying that they were sitting on the side of the road while he went and collected the bikes. Turns out, they were flagged down by another motorist who said that something was dragging and throwing sparks. The weight of the bikes twisted the bumper and let them drag down the road.
I'm sure lots of people do it without issue, but no chance that I am going to do it. I have a fifth wheel and need to carry 2 bikes now, 1 kid's tricycle and next year, my wife will start bringing her bicycle, too. So it'll be 4 for us. Right now, I just kind of pile them up on the dinette table folded-down with neat-sheets between them. Not idea, but it's what's working for now.
When I had my pop-up, I carried 3 bikes using a Thule Raceway on the back of our Durango. To carry more, I would have gotten Thule products to carry them on top of the SUV. Just prepare yourself for sticker shock - $$$. :(
