Yup, fell over yesterday. I had my 580 EX on my nano stand w/ an umbrella, everything was going good and then the slightest unnoticeable gust came along and blew it all over. The only casualty is the shoe mount clamp (busted right in half). My 580EX also got a tiny tiny scratch on the side of it. I feel lucky to have only lost the clamp (probably protected the mount on my 580EX by breaking).
Anyway, I went out and purchased two all weather 15lb sandbags to prevent this from happening again. The 15lb bags were $30/each which I thought was quite expensive, but the other option was 5lb bags which were $25/each and I would have wanted at least four of the 5lb bags which would given me 2/3 the weight for about twice the cost.
I'm interested to know if anyone has any thoughts on using one 15lb bag/stand outside. Is that enough? Too much?




