I'm going to try rod instead of tube for the tent poles. They are 8mm Fibraplex, about 25g per metre, so I can't complain about them. They've lasted brilliantly. But what if I tried 3mm rod instead? It's about a quarter of the weight, and bendy enough. I don't see why it should snap, it doesn't really do very much. Might as well try. I think the best thing about making your own stuff is you can risk very fragile constructions which the manufacturers daren't try.