I temporarily installed the battery and starter relays to the firewall using the outer holes that were already drilled through the firewall and stiffeners. I wanted to check to see how much play I had in drilling the inboad/center attach holes. Since there is plenty of flexibility to be able to adjust the relays based on the large slots in the relay tabs, I just measured and drilled the corresponding holes in the doubler on the workbench according to the measurements in the plans. I then drilled the doubler to the firewall and deburred everything. The firewall was then dimpled using the pop-rivet dimple dies and the doubler was countersunk. I also used one of the large nutplates as a guide in drilling the corresponding rivet holes to attach these.
Trial fit relays to firewall - plenty of play for drilling center holes in doubler
F-7127D relay doubler drilled and clecoed to forward side of firewall
