- and Roush, I'm surprised at you, you normally speak a modicum of sense!
well you know I could give matt some training advice as well , like perhaps-
matt you may want to focus on myofibrillar hypertrophy at least once per week as myofibrillar hypertrophy as actin and myosin contractile proteins increase in number and add to muscular strength. and a stronger muscle can become a bigger muscle. But only once per week just for those strength gains, because a majority of your volume should be focused on sarcoplasmic hypertrophy, where the volume of sarcoplasmic fluid in the muscle cell increases and will result in a 'larger more swole' muscle cell and a fuller and bigger bicep muscle.
you may also need new muscle stimulation and thus 'shock' the muscle into a new growth phase, as muscle is adaptive in nature and can be forced to grow and adapt to new stimuli and stress that is put on the muscle from mechanical tension. as mechanical tension increases the muscle needs to adapt and 'grow' to deal with that tension and new stimuli.
so matt you may need to mix things up a bit, add in more volume based training with higher rep ranges on the sarcoplasmic hypertrophy days,, can be accomplished by adding drop sets, super sets, giant sets, as well as more TUT time under tension- which is more easily accomplished by using cables as the cables have constant tension, on a fully contracted biceps muscle (both brachi long and short head) and a fully lengthened biceps muscle, whereas free weights, because of gravity, don't have constant tension.
I'd save the heavy dumbbells and barbell curls for the once per week myofibrillar hypertrophy days, where as the majority of your volume and sets can be done on cables and machines for more mechanical tension/volume/TUT (which are all very direct mechanisms for muscular hypertrophy).
also for more stimuli, in order to 'shock' adapt the muscle into new growth there is blood flow restriction training which can help 'volumize' the muscle and it will appear bigger and fuller.. volume is still key , so you may want to dedicate a full day to just biceps and triceps (don't forget triceps make up the majority of your arm size), but on top of that you can do additional volume by hitting biceps again after a back work out (being the biceps become a secondary muscle in a back routine) and hitting triceps again after a chest/pressing day (being triceps become a secondary muscle in a chest routine).
things such as ^^ those can add new stimulus to the arms and force the arms to adapt to that new stimulus and thus grow (thats how muscles grow through training).
so there you have some training advice , ok Big Ben, I got that in my bag too
but, I still stand by the simple fact that too, that if Matt focuses on training his arms hard, and at the same time tries to add on more size and mass to his frame via 'clean bulking' (gear as part of that), that his arms will follow. If he adds 30 pounds to his frame, while focused on training arms, that his arms will indeed be bigger.