I see you have 2 screws added at the top of this frame brace. What did you screw into? Pic?
I added a photo of the back side with the screw location.
I drilled through into these braces, then just used a 20mm m3 screw/nut to connect the two... http://www.thingiverse.com/thing:1872162
I can try to get a pic tonight.