Using speed lights has it's benefits but using them with light modifiers is not one of them. Up until a few months ago I thought the only options I had was one of those umbrella brackets with a thousand adjustments. Other than being like a Rube Goldberg device their main drawback is that the center of the flash is not aligned to the center of the modifier. But I recently discovered a nifty little item that has changed that.
One day while I was browsing on eBay I came across something called the S-type flash bracket. It's a one piece flash attachment that will mount to pretty much any light stand. For the modest price of around $30 I had to try one out. After a few clicks and a week of waiting on shipping I had one in my hands.
My initial impression is that it was well made, even though it is made out of plastic. But as I discovered this bracket has many advantages. As I noted before it keeps the flash center aligned with the center axis of the modifier. If you recall from college algebra it's important for any parabolic device to have the light source in the center and at the right depth, which brings me to my next point. You can adjust the depth of the light into the modifier, with the length of the flash head being the limiting factor.
The next thing that I love about this bracket is that it will accept any Bowens mount modifier! So any studio equipment you have can now be used on location. Keep in mind a speed light may not have enough power to fill a 7' softbox but you could theoretically use it. You will want to use sand bags or some other means of making sure your stand doesn't fall over. If you have umbrellas you can still use those too, and the head of the flash will align with the center!
Another cool thing I discovered about using this bracket is, by mounting the flash on a clamp around the head of the flash you aren't stressing the foot of the flash. This is especially true if you also use a wireless trigger.
I discovered with my old bracket that the triggers I had wouldn't fit with the flash in the correct position. So, I mounted the flash backwards which made it difficult to adjust or see the power settings on the flash. I have only used this bracket with the small pressure mounted softbox I got to use with the first type of bracket I bought but I plan on ordering a Bowens mount octabox soon. I will update this post with the results.
So to summarize, I would highly recommend using these brackets if you use speed lights. For about $30 you can't go wrong!