Yesterday, I prepped the fuel level sender and trial fitted it per the plans. No issues.
Prepped the parts for the fuel window today. Found out I did not have to drill the plexiglass to #27 as the holes were correctly sized. I did have to drill tank itself and the window backing plate to accept the #6 screw. This is not in the plans.
Roughed up the rivet hole area in the fuel window with some coarse grit sandpaper and scotchbrited the metal backing plate. Cleaned the metal mating surfaces with naptha. Did not use naptha on the window as I did not know if it would react badly. Was careful to avoid getting any oils on the plexiglass surface.
The window uses the tiny all metal locknuts. I ran the screws thru the locknut a couple of times before installation as they are very very tight.
Mixed a small batch of fuel tank sealant using the gram scale. Placed a thin layer on the window and then attached it to the top two screws (temporarily inserted). As I dipped each of the screws and tightened them just snugly, some of the sealant oozed to the view holes. It really just takes a THIN layer of sealant. I tried to clean one of them up a bit and made the situation worse. Nevertheless, it looks OK.
Used a small hemostat to install the 4 washers at the required locations, all at one time. Mess-free.
Finished by drilling the tank flange.
Time Today - 4 hours
