Training the upper pecs is a good way also to push the lower pecs, adding thickness in the upper can only results in making it easier to grow the lower portion after.

My first trainer in 1986 noticed I had lagging upper pecs, he put me through :

Wide grip incline Bench press
Narrow grip incline Bench press
Incline DB press

Just for a blitz 8 weeks, the uppers pecs just popped out very fast. I would not do this more then 6-8 weeks though.

Eric