A huge natural bodybuilder I know, who I know for a fact is natural because he is an Evangelical Christian fanatic, told me that the key for mass is coconut meat. Fats are great for mass because they're calorically dense, but saturated fats, although being awesome at boosting testosterone, are not ideal because they hamper digestion and increase insulin resistence. Coconut meat is ideal because it contains lots of unsaturated fats and good saturated fatty acids. The man is 5'10 and 240 lbs. He's not ripped, but his bodyfat is probably just about average.
SUCKMYMUSCLE