Diogo, I too shoot 3 under, and had a similar problem when I was anchoring with my index finger. I switched to my middle finger at anchor, and that seems to keep my lip happy. Also, I switched to a glove instead of a tab, so that there is not a leather edge on my lip. If you can tolerate one (a lot of folks don't like gloves), give a glove a try out may help. Good luck, and happy shooting!