It's been a while since I worked on that piece, but as I recall it is basically a tooling hole that is used on the right (?) side for the cockpit overhead light wiring? On the other side, I just filled it with a rivet. My RV-12 is out in the hangar so I can't say for sure. YMMV
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 (circa 1965) - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B 2020) - N124DH flying since March 2014 - 1,110+ hours (as of Jan 2022)!
through June 2022.