I did something like that for my son - he has a 1979 VW camper bus they use a lot for camping. Yes use a stabilizer on the back. I like the Pellon tear away stabilizer. The satin stitches will crinkle & pucker the background fabric if you don't use it. And if you're unhappy with the bumper, then yes replace it or you'll never be happy with it whenever you look at it!! It's really cute!!! Good luck & I'm sure your son will love it!!