It comes down to the shape of your muscle as determined by genetics. There is little to nothing that can be done other then to make the entire muscle bigger.

Pushdowns with a reverse grip theoretically hit the outer head more than any other movement, but they hurt my wrist.

Try close grip benches with strict form. Your arm shape is genetically determined like Aboot said, but if you feel no soreness in your outer tricep, you need to switch movements around until one clicks.

I use kickbacks for the lateral head sculpting.

Try this for more info
http://www.etricep.com/horseshoe-tr...h-superset.html

okay, good guys, i've been doing the reverse grip for like 6-8 months now, it's just become a custom, i heard it worked better, and since then it's just been that way.
My tricep is good size, it just doesn't have the lines on the outside that i want.
I was doing skull crushers tonight, and i found that keeping my elbows in on the chest press reps, makes the outter tri work much more, is this the technique required on the close grip bench?
I've been doing them much more like a regular press than keeping my elbows at my sides.
I also found that keeping my elbows together on skull crushers makes much more concentration on the tri

thanks guys