Mission complete! The piglets have been moving in on Pinky's nest since I removed the divider from between their pens - and they seem to have convinced her that three bodies are snugglier than one! Or, maybe it was just that Pinky had started using their prev nest spot as an elimination area that motivated them ... in any event, they all seem to be getting along well.
There is some bowl-hopping at feeding time, and Pinky has started bolting her food (and choking) in the rush to eat it all (I have a bigger bowl for her now, to slow her down), and I have started feeding Truffle separately, as he needs some condition. Will re-worm them this am, too.
But overall, the integration has gone well! I credit Pinky's basically good nature, the piglets' youth, and the fact that I didn't actually MOVE anyone's home turf for the smooth transition to group living.
Now they will all be able to enjoy the tree-canopied pig yard come spring - once they agree to venture outside again!