I never had a platform, but I did have one of these bike racks on my other trailer.

I got it because of the bouncing I had seen with the receiver style bike racks. There are 2 of these attached to the bumper (1 for each bike wheel). I never had any problem using it. This particular model held 4 bikes, but because of the spare tire, I could only put 3 on it. There is another version that holds 2 bikes, but we had 3 kids that wanted to bring the bikes.
I never had any problems using it, and the bumper never showed any issues. We used it for about 5 years before the kids moved out, and I just haven't put it on my new trailer. Since I only bring 1 bike now (and then it is only occasionally), I'm not sure I want the extra length behind the trailer.