I have made the coffin-style case.
I cut out plywood peices, glued the ectire box together and nailed it down, then cut the top quarter off for a lid.
Then I added some reinforcement at the corners, and where the hardware would be attached.
Then I covered the outside with a tolex-like vinyl covering using wood glue. Next I attached the hardware and some corner protectors where two of the vinyl edges met.
For the handle, I sewed some nylon webbing into a loop that cradle the case and screwed it to the body. I feel that this method is more stable than attaching a handle to the top piece.
For the inside, I used styrofoam to support the neck and to section off an area for storage. I cut a thin piece of plywood as the cover for this.
For padding, I cut foam pieces to fit the spaces I needed and made "pillows" by covering the separate pieces with fabric. To fasten the fabric , I cut posterboard to the shape of each pillow, and covered about a 3 inch border on the back with wood glue and let it dry. Then I layed the fabric face down, then foam, then posterboard (dried glue side up), then folded the excess fabric around the edge, onto the glue. Then I ironed the fabric over the glue, using the steam setting which softens the glue enogh for the fabric to stick, and then hardens. For the sections that were too small to do this to, I sewed the fabric around the foam.
Then I covered the compartment door (vinyl on back), and used a cloth hinge to attach to one of the styrafoam pieces, which were also covered in fabric.
Final step: Hot glue in the Pillows and supports and add some rubber feet.
Its a bit labor intensive, but I enjoy woodworking, and crafts, so it wasn't too painful. And sometimes you really need a case, but no one will give you a clear answer about if the oversized body on the bass you just made will fit into their cases.