Each apex of every point is identified by an X-Y measurement from the origin at the lower-left corner of the OSB. I just use a tape measure to set out each point and connect the dots. For the curves, I use a Rotape, a specialized tape measure with a steel pin that comes out of the center and a pencil lead holder on the end of the tape. You just pull the tape out to the radius you're needing and scribe a big circle. The tape is calibrated from the center pin, so you don't have to worry about the thickness of the case (unlike a standard tape measure).
Because the centers of these curves lie off the sheet in most cases, I had to butt a second sheet up to the one I'm laying out so there was a place for the center point. I'm going to use these first curve pieces as templates going forward so I won't have to use two sheets. Here's what a Rotape looks like.
The hardest part about using this thing was keeping the center point in the OSB while I was drawing the curve 50" away. I finally resorted to lightly hammering the center pin in a little deeper so it would stay put. It would have been much easier with a helper.
As you may recall if you've read this from the first post, I was originally going to project the images onto the OSB using my InFocus PC projector and then just hand-draw around the image, but the results were very disappointing. The images were too distorted to produce an accurate replica and would defeat the whole purpose.
As it is, even if my drawings are perfect, I'm still having to execute those longs cuts with the saber saw. My first curved pieces weren't my best effort. Before using them as templates, I'm going to touch them up with the belt sander. For the templates I'm going to hammer in some brads at the curve start and end points and just bump the template up to the brads and trace. This will be much easier than trying to hold the curve in place over the points which can be many inches apart.