Trade-offs, trade-offs. If you want an inexpensive 6x6 system camera, the Mamiya TLR will work. The weight issue is a bit misleading - the TLR bodies are heavier, but the lenses lighter than comparable SLR items.
Try http://www.macuserforums.com/WebX?38...iTF.0@.ee6b280 for the US Mamiya Forum. The Mamiya US site (http://www.mamiya.com ) needs Internet Explorer to navigate, so it can be hard to find the forum!
I have some weight comparisons, plus some other useful information at http://www.btinternet.com/~g.a.patte...faq/m_faq.html