Here's a suggestion. Keep the 124G - its a great camera, but if you want to try out a medium format SLR, how about 645? unless being not square format is a dealbreaker. I recently bought a Mamiya 645J to complement my Yashica 635. Both very different. I think you would miss the lightness and convenience of the Yash. However, M645J's are cheap. OK, only 500 shutter speed (enough) and no interchangeable back, but a very inexpensive way into medium format SLR. The M645J is *just about* portable. I walk out with it round my neck on a good strap and with a prism finder its certainly useable handheld, but I wouldn't want it to be any heavier. My yash 635 on the other hand, is no heavier than my 35mm kit.