I have painted on canvas for years. Recently I noticed that the canvas was bouncing a lot while I painted. Very annoying. Perhaps the canvases I used to paint on were stretched a little tighter. My local art shop has a new product (new to me). Painting board which consists of a thin plywood panel mounted to a stretcher-like frame. They call it a cradled wood panel. It’s quite stiff and reasonably light even though it’s available in some fairly large sizes.
I like painting on these panels. I gesso the board and flatten it as much as I can. If I want it flatter I could sand it; the gesso is apparently sandable. My latest painting is on canvas and it is clear that I like the board better. The board is firmer and allows painting fine detail more easily. I’ll attach a link to Opus but I bet these are available just about everywhere if you want to try it. I definitely recommend it.