I'm looking to invest in some macro gear for my Mamiya RZ67 Pro ii, and with my 150mm 3.5, I figure a couple extension tubes would do the trick. Does anyone have examples of the Mamiya offerings in action? I want to start with a single tube, and I get the feeling the 45mm would give me what I need, but I wonder what that minimum focusing distance would be. Any examples, advice, or general thoughts?