I read a article by Jim Wheeler on subcooling considerations. He states that a unit with a TXV should have atleast 10* of subcooling, but to achieve even greater efficiency charge until the liguid line temp. reaches the outside temp. or until you notice a significant rise in head pressure whichever comes first. I have a Rheem 12 seer 3 ton system with a TXV. I added refrigerant until the liq. line temp dropped to 98*. Outside temp. was 95*. Liq. line pressure was 295. That gave me about 31* of subcool. Is this system over charged or is it more efficient?