In your vintage all metal to metal on the inside was riveted. On something as light as draperies I would not worry about vibration working something loose if it were screwed in. In later years where the brochures showed a chandelier hanging from the celing in the lounge the manual said to use screws for attaching stuff to the inner skin.
If you use rivets be sure to use aluminum ones. Steel are very hard to drill out and can rust!
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato