Doing dips for the lower chest is about as effective as doing preacher curls for the (lower) biceps. This is a deeply entrenched myth in the BB psyche that just won`t go away and is continually perpetrated by the pencil neck geeks that write workout articles for the muscle mags.. It is (physiologically impossible) to contract more muscle fibers in one area of a (particular) muscle simply by changing the (angle) of an exercise. The muscle contracts by impulses sent by the CNS and these impulses cannot be redirected to a (particular section) of a (particular) muscle by simply changing the angle of an exercise. It is an all or nothing contraction and the muscle contracts as a (whole) unit. This is not my opinion but neurological fact.
Inclines do not apply to this. Although the upper pec shares a common insertion point at the shoulder, it is a separate muscle and will be stimulated more by a different angle (an incline). It is easy to understand the misperception that if inclines work the upper pec than a decline (the opposite of incline) will work the lower most section of the pec.
Dips are (one) of the best pec movements there is and will give you a greater ROM but it will not "build up" the so called "lower pecs" anymore that flat chest exercises. You can make a muscle bigger but you cannot alter the shape of it. This is predetermined (unfortunetly) by our genetics.
Pump on .....