Just a couple of thoughts on this:
1. If you mix ammo, and the SHTF, a grand jury, DA, or even the police may consider that to be either a sign of carelessness in ammo selection, or alternatively a sign of wanting to make sure you kill the other guy by using different kinds of ammo so in case one kind doesn't do him maybe a different configuration will.
2. If the SD ammo is of reasonable quality, it most likely will have been developed specifically for the purpose of self defense. IMHO, it is better to find one type of ammo that you can shoot well and fill your magazine with that.