Agree 100% Edwin. We have not experienced a tendency to tip when someone is sitting in them, just when moving them. But I'm sure someone someday will lean back and then..........
I also worry about the grain pattern at the curve where it hits the floor. Didn't do a very good job of laying these out - should have tried to make the grain straight at that point, if possible. Next time I try something like this I'll laminate the legs I think. I'm worried that sooner or later I'm gonna loose a piece of the back of the leg at the floor. But I'm 72 so I'll take the over on this one, and let my kids figure it out.
Stand for something, or you'll fall for anything.