Wizkid,
i have this same problem, genitically you may have an unfair advantage........ i mean, your lateral head my not ever grow as proportional to the long, and short heads....... the inside of my triceps is just pure beef,....... i gotta give GOD props for some great genetics....... but the lateral head is virtually non-existant. if i had to guess..... i beat you have a high peak on your triceps too dont you?........(just incase thats not specific....... the apex of where both sides of the horseshoe meat).
no matter what way i turn my hands, elbows close to the side or flared, my long head will take over. by doing press downs with a rope and seperating my hands about a foot at the bottom.
maybe that will help........( oh yeah, kickbacks work too, but i cant lower myself or my standards to do them...... sorry i dont mean that personally to anyone who does them, thats just me)
X