I don't change my stance much between boards. I use a wider stance on my park board. The width changes from around 21.5" up to 23" depending on the board. I prefer 22" though. I really like 12/-12 so I keep that the same on every board. I keep the bindings centered too because I ride as much switch as normal.
The Cobra is more fun with a little narrower stance IMO. When I first got it, I set my stance at 23" and it didn't float in powder as well as I thought it should and the outside of my feet hurt. I narrowed the stance for the next ride and now I love it. I know it is not a powder board, but that is what I use it for. I was at Wolf Creek last Nov for the 42" dumping and the Cobra was fantastic.