Hitbox issues

I'm going to get straight to the point, I have a 3d model that is smaller than a block (7x11x2 pixels) and what I want is to be able to put a correct 
hitbox for  the size but when I put everything, the min data ignores me and is not applied Even if I put something on it, it still detects 0, does it 
happen to someone else or does someone know how to solve it? I am in 2021.1 but with a plugin to be able to mod in 1.12 btw