However you can - depends on the design of the bags. Also depends on if they are needed to provide weight balance for what's connected, or if needed to deal with wind. At the end of the day, it depends on the design of the bags and the stands.
I've used portable chairs (in their nylon carry bags) and cement blocks, too. Just depends what one is trying to accomplish at the time. I only use stands that can handle the weight I'm putting on them, but wind is another, more unpredictable factor.
I think I should clairify my question. I have a B&H Impact heavy duty lightstand, a 60" Impact umbrella and a Morris dual mount light bar/umbrella unit. I am mounting 2 SB-600s on the light bar. I position the umbrella and lightstand so 2 of the legs are positioned to support the off balance of the umbrella. The whole unit seems to be very unstable.
My question: Do you fashion some sort of attachment to the center column of the lightstand so that the sandbag can be center loaded or do you drape the bag over the leg opposit the umbrella, or should I have ordered 3 instead of 1 (bags)? The stand has no provision for hanging a bag.
I'd drape the sandbag over the leg opposite the umbrella. Having more sandbags would probably be better, but even then it's probably not a perfect solution. I think this is why people prefer C-stands for their heavier setups.
The B&H Impact C-stand is very affordable at around $100. This is a lot cheaper than the brand name Avenger and Matthews C-stands. I have found them to be very sturdy and I suspect they are just as good as the brand name products. I guess the only negative is that they only come in one size and that is big and heavy, but these are not always negatives when you want to mount expensive equipment on them.
I usually use 2 sandbags on the leg opposite the umbrella as far out from the center as possible. I use either 48" or 60" umbrellas. I think anyone that has ever used umbrellas on location outdoors has had the pleasure of seeing the umbrella go crashing to the ground from the slightest of breezes.
A 60" umbrella is a lot of surface area for the wind to catch. Wind is a powerful thing
I have been using the Impact standard /light duty stands with the 45" umbrellas. Bought the 60" and the heavy duty stand thinking that combination would be the equal of the others. Found out that the 60" puts the heavy duty off balance far more than the 45" does the light duty stand. Not sure that I made sense, hopefully you get what I'm trying to say. I ordered one 5 lb. sand bag, which hasn't come yet, if it's not enough I'll get a second as you recommend.
I also have some 15 lb ankle weights that I use on occasion. The have the advantage of being "wrappable" and "strappable" can be secured rather than just draped (although I usually just drape them also).
On my light weight location stands, I can wrap them around a leg opposite a 45" umbrella or small softbox (18" shoe-mount) - sort of between the main upper extension staft and the and the support brace on the leg.
I like them for this purpose because I can move the entire setup around and the weights stay in place.
"I also have some 15 lb ankle weights that I use on occasion. The have the advantage of being "wrappable" and "strappable" can be secured rather than just draped (although I usually just drape them also). "
Not familiar with these. Do you mean they are bendable, as in you can twist them around the leg?
Since I first wrote this post, I've tried the center of gravity and the opposite the umbrella methods. To me, the opposite the umbrella seems to work the best. That seems to utilize the fulcrum principle, a smaller weight having a larger effect. What the heck do I know.