I don't know about chuscks at medium rare. Try it and see how it comes out, but I'm betting it will be tough. I normally cook them either for pot roast as Thirdeye suggested or i cook them to 300 or so to either pull or chunk. For slicing I would be tempted to cook to 185 or 190 like brisket.
maybe the medium rare is a bad idea. Sounds like faux brisket.
Was plannin on eatin with taters. I see everyone doing these and thought I should join in on the fun. Maybe I should just treat it like a brisket. I guess I will go with the "She's ready when it slides in easy" method.