Well in a postbac program, informal or formal, you're basically just taking more upper division science courses...and it might cost more to do (at a formal program or through open enrollment) or be more trouble since you have to apply to a program. I would stay another year at your undergrad college if you're not above the unit cap. I would have done that if I didn't already graduate because after 4 years, you're already familiar with how things are at your college. I agree about not overloading on science classes. Yeah, the more you have, the greater potential of increasing that gpa, but you want to do well, and that is the key thing.