I can understand your want to get to a lower weight given your height (you'll def be fighting taller fighters at middle and higher), and your previous experiences with it. Best bet is to just start training and cleaning up your diet and see where you end up. You're not new to hard work, so you got that covered. The deal is, being at 30 it might be a bit tougher this time around to get that low..but you'll never know until you try, right?