Loyalist Dave,
For what it's worth, when I was playing with these kind of loads with my 28ga/.54, I got better patterns when loading the PRB on TOP of the #4 buck than when I tried loading the buckshot on top of the PRB. Either way, the accuracy of the PRB was unaffected.
Tennessee.45,
Based on my experiments, and YMMV, but IF you insist on multiple projectiles for something that may want to take a chunk out of you, I would just load two PRBs and call it good, but I have never had a problem using my .54 on a wild hog, or my .50, (or even a .22LR). I'm actually planning on taking my .32 with a PRB out for them this year sometime, and will report if I get one. It's just a matter of placement, which I know can be challenging when a boar (we are talking Boars, as in wild pigs, and not BEARS, right?) is heading your way, but I'm not bright enough to get out of the way so never worried about it. Besides, in about 20-25 years of hog hunting, I have been charged twice, so not a very common occurrence if you're smart enough to NOT get between a sow and her young. I'd honestly just work up an accurate load aI trust and just use it for everything without worrying about anything except placement.