I have just bought a Vinten vision 3 tripod for a camera weight 3-4kg - depending on how much gear it has on it. The spring is very strong and needs changing to suite the weight. However no-one seems to stock the springs any more. Any ideas where to get one - or the specs of the springs to get one made. Vinten don't seem to have a good support service.
I got my spare springs for different tensions direct from Vinten for my vision 3 - Different colours = different camera weights and there was a chart on Vinten's site.