When I built mine I designed for a very long time, I tried different materials and settled on an aluminum extrusion that bolts together, but even with that, make sure your design, particularly the bed, is rigid and stable. I highly recommend you get a film holder and build to fit it, don't try to build a camera and hope it fits a holder into it. And give yourself plenty of bellows. If possible, do not try to get every possible movement into the camera design, this will make it bulkier and less rigid. I can't stress rigid enough. These things bounce around like crazy with the slightest breeze if you didn't build it rigid enough.