Ok mate, because I'm a nice guy and you sound like a hard worker in the gym I will help you.
My arms are just under 18", training well under 2 years natural, and I dip nowhere near what you can. But the reason I have decent arms is because I work very hard on them. TBH, to get any bodypart good, you're gonna have to work hard, unless you're blessed genetically, even then it'll need work.
My advice, is this, because it works for me, and worked for others too. Biceps and triceps are small muscle groups, and if lagging, you can train them more frequently and with more intensity. What I do, is finish triceps off on chest day with 6-7 quality sets to failure, cable pushdowns (3-4) and rope pulldowns (3). Rep range is 6-12 and I start heavier then pyramid down to higher reps. So for 4 sets of an exercise I'd typically do 2 sets heavy, 1 medium, 1 lighter. I then do similar but 4/5 sets for biceps.
I then have an arm day. 3 exercises for triceps, 2 for biceps, but quite a lot of sets. Dips, Tricep Pushdowns on the machine, then Rope Pulldowns. 6 sets dips, reverse pyramid 5-10 rep range, 4 sets pushdowns 8-10 reps, then 3 more with the rope (10-12) with a triple drop set to finish (ouch ...).
With biceps, I do 5-6 sets of DB Curls, very heavy. 3 sets in the 3-5 rep range, then 3 sets 5-7 rep range. Then I go onto a preacher machine my gym has, and do 5 sets: 3 heavy (7-8), 1 medium (9-10), 1 lighter (12-13) then a triple drop to kill them completely.
Yes this is demanding but that's how I train, balls to the wall. Remember diet and genetics are important too. But in all honesty, it's just a case of working them harder: More sets, more volume, drop sets and doing them away from chest/back days so they are fresh and capable of more.
Good Luck
MM
<message edited by Mad Manic on 26 July 2008 01:03>