Have you tried gum? DS9 was a chewer to a lesser extant and we found that gum helped. We use a xylitol gum so that I don't worry about his teeth. You might also want to consider a sensory "chew" toy or necklace designed for kids who need to chew. Given the amount of chewing you are seeing and the times you are seeing it, I'd consider that this could be a sensory need versus a bad habit. In that case, you are much better off redirecting it into a more socially-acceptable behavior than trying to shut it down. Logic won't help in those cases- even with smart kids.
