My sister, who is a vet tech, emailed me and said not to be too concerned with the attachment Percy has to Winston. I'm choosing to take her advice and am reminded again that you really can find someone, somewhere, to side with you when it comes to parenting issues!
I did take Percy out by himself today though, because I can see how the dogs each need their special time (this is what parents of multiple human children do too, right?). Who was crying when I took Percy...Winston! Percy was perfectly happy, but Winston was distressed. I'm sure the tables will be turned when I take Winston for his time. Percy and I worked on some of his behavior and went for a short walk. When I returned Percy to the crew there was just way too much excitement and some dominance demonstrating from Winston. A few minutes later Winston was still too excited to sit, but Lucy and Percy were cuddled together. Earlier this morning I caught Percy and Winston cuddling - Winston with his head on Percy's back. There's a lot of love in that little trio.
So in my quest to take advice/criticism with a grain of salt, and to listen to my own intuition, I feel good about today's efforts. Percy, Winston and Lucy have their own funky relationships and instead of trying to fix them, I'm going to give them each some time away from the others, but also let them work things out on their own.