While it's true you cannot really pinpoint outside or inside chest, the fact that chestmuscles have separate attachments at different angles, we can choose to develope the strands that mainly run from inside to out instead to up or down side of the chest therefor:
low incline flyes ( 15-30 degrees) and low-incline dumbell presses
try this chest program:
session 1-4
10-8-6 incline (30 degrees) dumbell press
10-8-6 incline (15 degrees) dumbell flyes
10-8-6 flat dumbell press
10-8-6 decline dumbell press
session 5-8
10-8-6 incline (30 degrees) dumbell press
10-8-6 incline (15 degrees) dumbell flyes
10-8-6 decline dumbell press
10-8-6 flat dumbell press
session 9-12
10-8-6 incline (15 degrees) dumbell press
10-8-6 incline (30 degrees) dumbell flyes
10-8-6 flat dumbell press
10-8-6 decline dumbell press
session 13-16
10-8-6 incline (15 degrees) dumbell press
10-8-6 incline (30 degrees) dumbell flyes
10-8-6 flat dumbell press
10-8-6 decline dumbell press
You wil be using very basic proven exercises for basic repranges. While we devote a few sessions to make progresse in a particular exercise, some juggling in the exercise order will provide a continued stimulus for your body to growth.
After 8 weeks of mass training it is advisable to do 2 weeks of specific tendon training (thicker tendons allow for more muscle to attach to them and to make progress in strength / prevent injuries)
No matter what reps you are using for tendon training they seem best trained when using the same weight for multiple sets and trying to complete the same amount of reps as in the first set
(very exhausting)
Example:
pick a weight you can do 10 reps with and do 6 sets of them, reps will gradually fall as u get tired....
for a BB seeking hypertrophy it is not advisable to do tendon traiing with LOW reps, like 5-6 reps as they are not used to work in this reprange, this would be more fitted for powerlifters, also while a constant weight is causing less hypertrophy than increasing weight each set. It is better to do tendontraiing in the "zone" to be prepared making new gains in mass and strength after that.
In your case tendontraining:
WEEK 1: TENDON TRAINING CHEST
incline dumbell press 6 * 10 ........
flat dumbell press 6 * 10 ........
(reps drop gradually each set , like 10,9,9,8,7,6.... weight stays same)
WEEK 2: TENDON TRAINING CHEST
incline dumbell press 6 * 8 ........
flat dumbell press 6 * 8 ........
Now get back for another eight weeks on your regular mass training program and taste the fruits of stronger tendons by being able poush more weight around.