I don't think I'll get anything bigger than a 70-300 - I shot a few test shots with the mirrored 500 with a tripod collar and the balance seemed fine - But I sure like the stability of this old timer. If anything I will upgrade the ball head.
Mogul wrote:
4kg = 8.8#
7kg = 15.4#
I've seen people put large format cameras on a 10# head; I'll stick with a 20-25, not because my Toyo is neat that heavy, but because of the torque at full extension. For 35mm size, I don't think it makes any difference with a short lens, but, with a 100-400 or 200-500, I'd want a strong head.