| do a full body workout 2 times a week. That would by far be the best option. You will work all muscles 2 times a week so you don't have to neglect your lower body.
Also, lower body lifts like squats and deadlifts put mass on the entire body due to the heavy stress they put the entire body under. When the body is put through this kind of stress it releases hormones, growth hormones that makes your muscles grow bigger. | 
