I think over penetration is like printing, people overthink it.
Remember there was a time when a 4" .357 was the cats meow when it came to defense.
So a .380, 9mm, .40 or a .45 with a quality hollow point shouldn't over penetrate. if it does more than likely there wont be enough steam left in it to hurt anyone behind your target.
misses are a bigger concern than over penetration in my opinion. carry what your good a shooting and practice.
Also remember Ballistics Gel is NOT a representation of a human body. its only to give scientist, ammo manufactures, feds, ect a consistent medium to test ammo in. if you want something more consistent with a human body do a layer of denim, cotton, pig skin with some fat, pork ribs, some fruit or other semi porous material and then another layer of pork ribs. results can be surprising.