After priming the fuel doubler plate, I could now install it to the firewall using 6 AN426AD3 rivets. Then the AN fitting was inserted, a 6D spacer went over and thightened the AN nut. Looks neat and clean

Here is a view from the inside. Fuel will come straight up from here underneath the center cabin cover from the output of the Andair boost fuel pump.

Next I prepared the firewall recess for final installation. It took me a while to decide for final installation as things become much less accessible once the firewall recess is on.
I'm committed on hanging the engine soon so it has to be closed anyway.

The initial fit showed I had to do some bending and reshaping on the tabs as the leave a gap.

Then noticed the 3 rivets that should first be placed on the side of the recess. 2 on the bottom and one in the middle.
Drilled and dimpled the sides and then squeezed 3 rivets in. 

I also noticed I forgot one AN470AD4 in the bottom of the angle that attaches the upper panel rib to the firewall angle. This is also the beefy angle that supports the forward canopy support of the roll bar. It would be difficult to set it once the recess is on. I was quite happy that I could use the squeezer to set this one. I hate shooting AN470 rivets with the gun.

The squeezer did a good job on these AN470AD4-7 rivets

Then I got out the 3M Flame master tube, degreased the parts and evenly spread it out on the contact points

Clecoed the recess in place and applied more sealant in the joint points where a gap was remaining.
You want it all sealed well to avoid getting exhaust gas fumes (carbon monoxide (read as: "death")) out of the cockpit in case of a exhaust break or leak.

This is how the recess looks from the inside

This will have to cure now and next I will be rivetting the recess on.