The best way of supporting beans that I've tried is to fix an old bike wheel horizontally on top of a post and then push canes into the ground in a circle round it and tie them to the rim of the wheel. I think my OH fixed a flat piece of wood on the end of the post and fixed the wheel to that by stapling across the spokes. I had 15/16 6 foot canes on each one last year. I should think 4 feet high would be enough for the post, though ours are about 5 feet. It makes a really stable structure. I've tried 2/3 other ways of doing it but this is the only one that hasn't blown down when we've had really windy weather.