I used the clamp and screw assembly from Cup holder table clamp by seilgu - Thingiverse and attached it to the panel brackets. Attach to the panels with M3x16 screws and nuts as before.

You can add a TPU pad to the screw and clamp to strengthen the grip. 

Don't overtighten the screw or the clamp may break. I found the screw didn't have to be too tight to get a good grip on the table.