Metplat size apparently does have a considerable bearing on effect in leathiality and penetration. Google, Michael of Oregon I think it is. he has done very extensive experimentation on this. His bullets -they are solids and jacketed - are shown to penetrate as good or better then the Woodleigh Hydros. He found, as well, that the metplat can be too big.

I just know from personnel use the flat nose 30-30 pills kill above their weight and noticed a wider metplat was more effective then the smaller metplats.

Interesting reading on peoples experience with cast bullets and having them expand.