We have had several photographers ask if they could use their Elinchrom Quadra in a FourSquare Box. The answer is yes. It is a very easy mount to solve with just a mini mount and a stud that comes with a 026 Manfrotto Stand adapter. You use a mini mount and screw it into the stud and you are ready to go. Like the image on the bottom left.
The top three images and bottom right use the same adapter but mounts a single head into a center mount on the FourSquare Block. Either way works. The most even light comes from mounting the head on the center mount and removing the reflector.