Not to mention the pec minor itself is a tiny muscle in comparison to the pec major, so even a 100% size increase (difficult to achieve for any muscle under any circumstances) would probably not have ANY noticeable effects. It's more akin to the serratus anterior muscles in size, but unlike them, it's covered by a much larger muscle. (The serratus can be seen when bodyfat is low, even though their size is small, because there is no other muscle on top of them. But feel for yourself... the serratus anterior will never get 'big'.)