There is a drill I saw on the golf channel where you pitch balls underhanded (right hand if your right handed) onto the practice green while making your normal chipping motion. I tried to find it to post link but I'm having trouble. Martin Hall was the one giving instructions and it helped me quite a bit. I do not know if this drill would be beneficial for you because you are light years ahead of me but you could give it a try if you have not already.
7/9/12 at 5:36pm