If you can find bigger chucks, but them. You can always freeze the leftovers. The smaller chucks can dry out too easily.
I agree with the colonel on cooking time. 3 hours per pound is going to be too long. Depending on the cooker temp and type of cooker they will probably be done in 75 - 90 minutes per pound. But, as you said, cook them until they are tender and a probe slides in like going into hot butter. For chucks, this is typically around 200 - 205 internal. If they get done early just put them into a dry, pre-heted cooler and insulated it with clean towels or clean newspaper. They will stay hot for hours. Also, the rest helps the juices and flavor circulate throughout the roast.
Foiling is up to you. I do foil mine and usually do so based on the bark color more than a specific internal temp. When the bark gets to the color that I like I foil with some sort of liquid. Beef broth seasoned with granulated garlic, granulated onion and some rub is a good choice.