I am looking at the Proaim mattebox for the 7D, and have seen a few users' rigs with them on it. It looks like it would be adequate for my needs. However, I am confused as to which one to get. There is a jumbo mattebox, a v11 mattebox, etc. I want one that sizes well with the 7D and has the additional side flags, and is able to mount to rails. Anyone have any experience with these and know which one is best?