A friend of mine has both a 212 and a 220 for his grandson. They both shoot the accutip with excellent groupings. As far as terminal performance goes, from what they have told me, not a deer yet has went more than 20 yards after being hit with either the 12 or the 20. You have that much weight hitting into a whitetail, there is no need for a partition. As long as you have done your part and hit it where you are supposed to and not at TOO long of a range, you will find that those accutip's will drop any whitetail on the planet.
You said you got better groupings from the accutip, then I would stay with them. Accuracy is the key. Not some need for armor piercing magic bullet. At the speeds your normal 3 inch firing shotgun slugs will go, it is HIGHLY doubtful they will break up.