I decided to bite the bullet and rivet the firewall recess. I purchased some high temp sealant, applied it to the opening and clecoed the recess in place. I let it sit for an hour per the directions and riveted the recess to the firewall. While preparing to install the heat vent box, I realized that I had never drilled the #10 hole for the control cable through the angle surrounding the recess. It would have been much easier to do this prior to installing the recess but it wasn't impossible. I sealed the heat vent box opening, bent the control cable end per the plans to attach to the vent arm and bolted the apparatus in place. I decided to use a "3" size adel clamp behind the bolt on the outside of the battery box to help hold the push/pull cable as well. I upsized the AN3-4A bolt to an AN3-6A to account for the additional thickness of the clamp. I hadn't installed the single lug platenuts at the top of the firewall recess for the oil line prior to riveting in the recess. Oh well. I drilled the platenuts through the recess, firewall, and angle and countersunk the recess for the AN426 rivets. -6 seemed to be the perfect length. Once I locate my Titeseal (I hope it's at the hangar), I will install the oil line to the AN fitting on the transducer manifold.
