I guess these aren’t really springs, but I am not sure what else to call it.
Anyway the big one is about 12" tall, and is approaching the practical limits of the technique.
It is very wobbly and the ends rotate easily if you grab them and twist.
It has maple “slats” and plywood for the ends, and is just press fit together without glue.
The small one is only 6" or so and it is surprisingly strong.
I can stand on it as long as I don’t rotate in its vertical axis.
No glue there except in one spot where the maple top piece split along the grain when I was putting it together. (which is why I switched to plywood for the larger one)