Covered the speaker mounting board with the thinnest foam I could find, then glued it in place. It will help keep the cloth nice and taught, as opposed to the old way which simply draped it over the board to get saggy. It's much the same thing as auto manufactures use on headliners, except that here the board will help keep the fabric tight.
First 2 pics I took looked exactly the same to the camera though they were completely different fabric, so I'll only post one pic to describe them both.
First a nylon or somesuch cloth, very thin but also very modern looking. I think it will clash with the fact that this TV is from the 50's, since it's something you are used to seeing on cheap 90's throwaway electronics. Soundesign or Spark-O-Matic ring any bells? Not very classy at all, definitely 3rd on my list.
Second one was something called 'Duck', but it just looks like plain black canvas to me. This was a heavier fabric, and didn't seem to fit in either. It didn't look bad at all, just that I think it's woven too tightly for this application. My second choice.
Finally, what I thought would be my last choice actually ended up being my first- plain black cheap ass burlap. Now this is something I had not considered at all, but got it anyway for comparison purposes. I actually ended up liking it the most, because the fibers are farther apart just like the original was. It's neutral, doesn't draw attention and it's something I could actually see RCA using on their sets back in the day. Maybe I could find a big gold 'Deluxe' script for the middle, what do you guys think?