Jim, the area where those ribs come from have a lot of connective tissue that will need to break down in order for them to be tender. Figuring that you smoke them at 250 deg. you're going to go at least 6 hours for that 'melt in your mouth' stage.
Apply your favorite rib rub and place them in your preheated smoker. After the first hour, give them a spray with a little apple juice and spray again each hour or so. After three hours, wrap the ribs in heavy duty aluminum foil and before you seal up the foil add 1/4 - 1/2 cup of juice to the ribs. Return them to the smoker and smoke them for two more hours. After the two hours are up, place the foil pack in a blanket lined insulated cooler, cover the foil pack with another blanket and let them rest til your ready to eat. [The ribs will stay hot (above 140 deg) for 3-4 hours this way.] When your ready to serve them, you can pop them on a grill and baste them with your favorite 'que sauce or just serve them naked and serve the sauce on the side.