Not happy with this result. Back to the drawing board.

My first attempt at adding the Grill cloth was a complete failure. Hopefully the 2nd attempt will
come out looking better. The method I tried was to staple one edge using 1/4" staples on the frame I made. The frame is about 1.5 inch wide poplar boards about 3/16" thick. I routed a lap joint at each corner so they are pretty strong and thick enough to staple the cloth and later the grey piping to. I first stapled one edge. I then stretched the fabric on the opposite side. Stapling from the center outward. Then repeated that on the other two sides. I think my problem was too much tension on the cloth.

(Not pictured) I was able to also Tolex 2 of 4 the back boards for the speaker cabs. The Other two I need to drill some holes for the speaker jack plates prior to adding the Tolex to those two.
I was going to wait to add the speakers after I had the plates done so I can hook them all up at the same time.