Interesting subject. Last time I ever did any serious curling was when I was playing college football and that's been eleven years ago. I couldn't tell you what they measured than or now but when you include the Big Boy exercises (squats, DL's, benches, dips, etc) the arm's tend to meet that requirement and get larger & stronger (along with the rest of the body) without any direct curling exercises. Of course doing a few curling/tricep press set's after a heavy lifting program is icing on the cake.
When 619Rules said that his power is in his triceps that would suggest that he has natural (genetric) stronger pushing power than pulling power. The triceps respones better to gaining muscular size. The potentionl for a 400+ BP, heavy pressing, dipping, etc is present. Guy's with a stronger pull (biceps) are usually the one's who do 360lb rows, two/three plate chins, etc. Their biceps usually respond better to gaining muscular size. Those very rare muscular, true steel tape measured 20/21" arms are helped greatly by a equal balance of tricep/bicep potentional. Not many trainee's can ever gain such size no matter how long or hard they train. Good Luck.