The door/windscreen pillar is considered rollover structure (and during kit development it was load tested).
Van's aircraft neither recommends or endorses drilling holes in this structural area.
What other options are out there?
Try flying without them, then see if you really want to install these or not. I'm in the camp that a visor is something to be removed, not added.
Carl
I've got a thousand pictures of the factory demo -10, but not a single shot pointed at the canopy. What is factory recommended?
That only works if you are over 40 and thus wear the baseball cap bill to the front!