Does using a larger slow cooker than called for by the recipe make a difference?
Size does matter in a slow cooker. In order for it to cook effectively a slow cooker has to be at least 2/3 full, other wise it cooks hot and will generally dry out faster. If you are cooking at less than 2/3 full you need to adjust your heat settings and/or depending on the recipe adjust the amount of liquid. Cooking meats becomes especially troublesome when underfilling because they tend to dry out and end up a lot tougher than expected. If you are cooking stews or chilis then simply adding more liquid to your recipe will generally work.