I made this gopro like mount in order to mount my stream deck to my sim rigg. It uses 6xM8 bolts and nuts so it has more than enough strength to support the stream deck XL. 

The biggest piece is supposed to be mounted to the rigg and has a 80mm spacing hole to hole (middle of one hole to the middle of the other hole.

The identical pieces are supposed to be the “arm”. They allow you to tilt up/down & left/right, however depending which order you choose to mount it the stream deck may end up in a tilt, see last picture, but for me that was no issue. The width of these parts are 25mm.

The last piece is supposed to be mounted to the stream deck and has a 48mm spacing hole to hole (middle of one hole to the middle of the other hole).

Thank you for taking interest, please let me know if you have any feedback!