Sizing Questions

I was going to order a pair of Union Bindings (not the contacts) and was wondering a few things about sizing. I am a size 7 Burton boot and was wondering whether I should go with a S/M size bindings or the M/L. The M/L does say it is for size 8 so will it be much to big for me to feel secure and comfortable in? Also any bindings suggestions would be awesome. I mostly do park riding. Thanks in advance.