6 superworms is a good and normal amount for an adult dragon if he's of a normal weight and eating his greens/veggies too. If he's a normal weight or under weight, then feed him as much as he wants, both protein and veggies.
Some dragons are good about regulating themselves and eating a good mixture of protien vs greens, and other dragons will be complete pigs about protein and then you have to kind of restrict how many bugs they get in order to get them to eat their greens/veggies. :roll:
How is his weight? If he's bordering on overweight, then that's the only time I'd personally cut back on the protein even if he wanted more (but offer lots of greens and veggies!)
I feel like I could have worded that all better, does it make sense? :lol: