I also have a KJ gen 5 P1 bio. I tried to fit it onto my DB 2nd gen. P1 mask, but it's a bit too small, the jawline and lower edge of the bio doesn't cover the mask completely.
Yeah, I heard DB sculpted it to fit the Morgan bio. Looks like there are other bios that work too.
This thread perfectly shows why sculpting bios and masks need to be done in conjunction with the corresponding mask or bio that will be used with it.