I upgraded my K8200/3DRAG printer with a 200x300 heated bed. (Write-up at: http://forum.velleman.eu/viewtopic.php?f=53&t=18449 ) The PCB was slightly larger than the working area, which meant that binder clips didn't work well for attaching the glass to the bed.
So I designed these corner clips to hold the glass securely in place with one M3 screw at each corner, using the existing mount holes in the heater PCB.
I printed these in PLA and they work fine, but it's probably a good idea to use ABS.
The two .STL files are the same design, but the second file has four copies to simplify printing a full set.