I'll recount my experience with vests as it's pretty extensive.
In 2012, I hurt my ribs seriously for the first time. I had been using a Tillett P1 vest and really liked it but after years of abuse it was worn out and wasn't really doing anything for me. In a qualifying session I popped a rib and then couldn't physically sit in the kart due to the pain. Doctor confirmed it was separated, meaning the cartilage and muscle (intercostals) had torn and allowed the rib to separate from the rib cage. Unfortunately, there really isn't anything you can do for this type of injury other than sitting and allowing it to heal. The worst part, is that if abused to much, these muscles and tissue grow back as scar tissue, making them weaker than they were before the injury. So over the next two seasons I basically popped my rib every race weekend and had to fill up on pain killers just to get through the weekend. I missed a lot of races and had to abandon a few in the middle of the weekend, including a trip to SuperNats. I tried out basically every rib vest, seat padding, and seat on the market, but couldn't really make anything work that allowed me to be truly pain free. I spent a lot of time experimenting with different layers of padding and adding padding to vests to help trouble areas. In fact, at the SummerNats in Dallas that year, I was leaning off my bad ribs so much that I actually cracked my ribs on the other side as well. So I was beat up.
Then in 2015, at the first race at GoPro, I was in excruciating pain after about 3 sessions of Friday practice. And this was after I had 6 months of rest in the winter. I was basically ready to abandon the weekend and seriously was considering giving up racing for a while as it was evident this problem wasn't going away. But then I tried out the Bengio Bumper vest. I kid you not, I went from being unable to sit in the kart from pain, to having almost zero pain in one session. I put it on and sat in the kart and instantly was comfortable again. No need for a special rib-protecting seat, no need to adjust my posture anymore. I went from being unable to drive a Yamaha on a green track to being pain free running X30 on a super sticky track. I ran RoboPong without issues, I ran a whole schedule of brutally grippy SKUSA/USPKS races in X30 with no issues. I would never race without it now. I don't have any relation to Bengio or anything, I don't even know where to direct you to buy them (I got mine on ebay from overseas), I just firmly believe that it saved my karting career and I'm super grateful I found it.
So if anyone ever asks, I always direct them to the Bengio Bumper. It isn't a complicated vest or anything, it just fits perfect, there's no pressure points, and the padding is great. I found some vests actually made my ribs hurt MORE because of pressure points in the back area, where my injury was.