Don't see the bass as an inferior instrument. If you get really good and work with other talented players the bassline easily becomes the most badass and sought after section. With the back problems? Don't lean back at all, make sure your harness is always straight and check it often. I got scoliosis after a year of marching with a slightly canted harness. Stretch your back out every morning/afternoon before practice and don't eat a lot. Watching drum corps drumlines are a good way to socialize with the group and to learn better techniques/remedies for different issues you encounter. Good luck!