Can these small strips of wood prevent the wide top from cupping? I don’t know, but they cover the end-grain and make the top look complete.
The breadboard end is essentially a tongue and groove joint with a couple of integrated mortise and tenons fastened with some draw-bored dowels. I found that the process of making them on the scale of this table top was a little easier than the practice ones I did on a small chess board (see this post here).
Breadboard ends make the final planing of the table top difficult as you now have grain running in two opposite directions. I planed the ends almost flush, but finished the job with a palm sander. This kills two birds with one stone as I had problems with tear-out in the mahogany and have to sand as a last step anyway (more about my tear-out problems here).
The outer edges of the table top were not parallel and still rough sawn. Because of this, I made the breadboard marking lines with a square using the center line from the glue-up.
I fastened the breadboard ends using 1/4″ walnut dowels I made using the Veritas dowel former.
The final touches to the top were to saw a curve into the long sides and bevel the undersides to make the top visually (but not structurally) more delicate. To draw the curves, I simply cut a long thin strip from a 2 by 4 board of pine. It was a two-person job though – one had to hold the strip to the marks at the ends and center of the table top, and the other then drew the curve with a pencil.