2x Speedlight to Neewer Softbox (circular studio mount)

I created this because I got some Neewer Softboxes for free and had no way to use them with a speedlight. You can attach two full-sized speedlights to the vertical bracket using collared 1/4-20 to coldshoe adapters from amazon with the 1/4-20 end screwed into the coldshoe stand that came with your flash.

https://www.amazon.com/Fotasy-SCX2-Adapter-Premier-Cleaning/dp/B00HPAPFNU/ref=sr_1_1?ie=UTF8&qid=1520155578&sr=8-1&keywords=1%2F4-20+to+hotshoe

I included the sketchup document in case yo