Re: the power robbing nature of sealed chains--there is some debate out there about how much power is lost when the chain gets up to operating temperature. On all of my other bikes I always run sealed final drive chains, usually RK, sometimes other brands, and have never regretted it. They just last so much longer that to me it's worth it.
I know that the primary drive chain on the P11 runs in an oil bath (sort of), but old habits die hard and I know I'm going to want to put a sealed one in there anyway. On the other hand, there was a Harley big twin back in the 1980's, I think it was, that came with an enclosed, oil bath final drive chain, and those things lasted a loooooong time, so I may yet talk myself out of a sealed chain. If I'm not mistaken, engine oil can be hard on sealed chain o-rings, so that's worth considering as well.
This P11 is my first bike that does not have a unit constructed engine, and although I've had bikes that transmitted power to the trans by chain, they have been Japanese ones (CB750, KZ750 twin), where the chain is a wide, hy-vo type that lives deep in oil all the time deep inside the engine. Owning a british twin is all kind of new to me and I'm excited to learn all about them and what works best.
Sorry for sending this thread down a bit of a rabbit trail!