What size binding for this board ?

I just recently purchased a rome artifact rocker 2012 150cm off evo.com. It still hasn't come in yet but I still need to purchase bindings. I've heard the rome 390's are good? So I think ok gonna get those unless u have any other suggestions. I'm just wondering if I should get the small/medium bindings or large/XL. I have a size 9.5 boot but it's a tad small so I'm going to get size 10's soon. They are the brand "thirty two". So the large/XL BINDINGS would probably be better but will they fit ok on my board? I have a -15/15 stance and if it matters I ride goofy. Thanks guys!