Trigger forward instead of back "Bear"

Bear,

My son has developed a bad habit of bringing his hands forward a little and stopping and then swinging from there which is totally diminishing all his power. He is a big strong kid with an otherwise very nice swing. I've always been able to help kids hit better but I'm a little puzzled by this. What we are doing is the 1-2-3-4 drill to get him to load with his hands and hips cocked or coiled and telling him to keep his hands back from the start and to concentrate on swinging from there. Are we on the right track and just need to be more patient or do you have any suggestions?