I am installing Doubletree spherical metal grommets for the firewall pass thru on the throttle, mixture and prop control cables. Each pass thru requires a large center hole plus six more holes for mounting screws. The grommets come with a paper drill template which I used to make a drill guide from some .063 aluminum. Drilled a #40 hole in the center and at each mounting hole location, then made #40 holes in the firewall at the plans location for the cables.
Used the squeezer to set the rivets on the F-6118 rudder pedal bracket near the firewall.