if your going to LST do both or your going to end up with one plant a foot or more taller than the other one which will be a nightmare belive me cus you`ll have to move your light up to acomadate the "tall" one and the LSTed one will be miles away easyer to just do both, 10inches is quite big have you not thought about just flowering, i started my grapefruit when they were about 8 and there about 4foot now, gettin cut tomorrow yipee!!