It's a great solution, Ken. I've seen originals with tabs in the barrel channel like this. He probably doesn't have any tabs left but could make another to fit.
With a little filing and soldering he could have all of the tab necessary to secure the thimble.
Reduce the thickness on each side of the tab, then solder a thin piece of brass or steel on either side and inlet. No big deal, and faster and easier than making a new thimble.
As an afterthought, you might fold a slightly oversize piece of sheet metal double and solder both sides of the tab at once. Cut or grind sheet metal at the bend, and you have a new thimble with a long tab ready to install.
You might insert a pin in the newly soldered tab and peen it for extra insurance, if you don't trust your soldering technique.
Just kinda thinkn'...typn' out loud, so to speak....type.
J.D.