Hi, 
  
I've purchased a GM1, and would like to mount it near, but not on, a windscreen. Refer pic. 
  
  
The windscreen has a rail that runs along the top, to which a sun visor is attached. It's about a 5mm steel rail. I'd like to mount a GM1 to this (was originally going to be a BMPCC, which had a top mount thread), but can't see a convenient way of doing this. 
Any suggestions? I'm happy to mount it upside down, and rotate the video in post if required. Basically I need something to go from the 5mm rail to the tripod thread. 
  
Thanks in advance 
  
David