Ritalin LA - Dosage HELP | ADHD Information

My son is nine and has been taking Ritalin LA.  His metabolism eats up meds, so he was on 40 mg X 2 daily.  The dose only helped him for 3-4 hours rather than the 8 it was intended for.  Since then, we've done a complete med wash and started back on Methylphenidate only.  The meds are soooo confusing.Started with 40 mg once a day. I could feel it wearing off after 6-7 hours.
Went to 20 mg 2x a day. Seemed to help. I went back to feeling the meds
wearing off and the scattered thinking along with mild anxiety. Just
started taking 20 mg at 4:45 am, another 20 mg at 8:00 am and 20 mg at
12:00. I'm feeling ok, getting things done - clear thoughts and organized.
The only side effect is tightness around my cheeks. Any advise will be
welcome. My Dr. says the 60 mg of Ritalin a day isn't too much.