I'm an ecto-endo (what a combo, huh?): ecto more on top, endo more on bottom. What works for me is heavy weights on top (P90X was excellent for this) with good recovery time. When I did a GS rotation, I did one upper body workout day 1, legs on day 3 and the otehr upper body on day 5, to give my upper body more rest and recovery time to grow and repair.
There's a lot of info out there on "hardgainers" (usually ectomorphs), and working out hard and RESTING is what is often recommended.