Bike rack on rear bumper

I had one welded on and it was safe and did a great job. BUT, the rack we used did not have a tray for the wheels to sit on which meant that they hung from the top cross bar and they swung and bounced and really beat the bikes up. Because of the bounce it was difficult to keep the rack attachments tight. They always seemed to loosed up which worried me. When we traded trailers we switched to an over the propane tank rack that we are much happier with. We can see them while towing, they don't bounce and I'll never have another on the back.