Here's a different idea: get a whole loin and roast it in the oven. Much less chance of drying out, plenty for 12 (if you have enough side dishes). You can even have the added effect of carving at the table.

Season loin with salt and pepper, and brown all over in a skillet. Let cool a bit, rub with herbs or spices, then cook in oven at 375 to 160 internal. Make a quick sauce with the pan juices. Mmm...

If you want to get even fancier, butterfly the loin and stuff it with something good.