When I started karting I had minor rib pain with a cheap vest. I switched to the Rib Tech and had Major rib pain. I was in horrific pain and didn’t know what to do. I went to a chiropractor friend and he took an xray to see if I had broken a rib. I didn’t but the xray revealed that I had one rib on my left side that didn’t line up. It stuck out past the others. Nothing really wrong just my anatomy. The Rib Tech vest which normally does a very good job of distributing the pressure evenly ended up being the worst thing I could have done because it was concentrating pressure on one rib. I found a K1 vest with more of a curve to it and I’ve been good ever since. My point is that the best vest may not be the best for everyone. If it doesn’t feel right don’t use it. As others have said stay out of the kart until your 100%. For me it took 5 weeks. The first 4 it felt like it was no better sometimes even worse. It seems to completely go away all at ounce in the 5th week.