We have decided to go with using the gray vintage connectors to hold the new pieces together. It is working very well and is compatible with the existing sets.
Above is the yellow triangles I made before, but with additional holes cut to accept the gray connectors.
Here is a new hexagon piece being connected to the yellow triangles with the vintage connectors. I haven't put any etching on the hexagon until I get a image or description of how the etching should look.
I was having fun playing with the new pieces.
Here is a square piece cut out of transparent plastic. The color is called "smoke".
The old and new pieces are interchangeable as shown here. I made a smoke triangle with some circles etched onto it with a center 5mm hole.
Here is the smoke triangle with some other vintage pieces.
Overall I'm very happy with these new pieces. Thanks to Chuck from the Micropolis Embassy with getting me hooked up with a vintage playset. Once I get the etching onto the new piece the Proto Playset will look very sharp!