Lack of appetite is a big complaint with the existing meds. Perhaps try to set up a rigid schedule for him to eat on - he won't initiate eating (no hunger) but usually even on the meds they'll eat what you put in front. If still he's not gaining weight or losing it many have found that the same powdered protein shake mix that weightlifters use does wonders. They have flavors like milkshakes and one scoop in a glass of milk can bulk his calories up.
Since concerta apparently works have you been offered to try Ritalin or the generic? They are inexpensive (off patent) and seem to help the most kids.
let me edit, he is 11 now and has been diag since first grade, we have tried many meds settling on concerta we are just getting nothing out of it anymore and he is losing weightThey say Adderal XR, because it is slow release, doesn't cause the zombie thing so much. Ask your dr.