Fuel Tank
The surfaces between the doubler Ring and Fwd Tank Bhd does not require tank sealant because when the cover is installed, it will be sealed and this sealant will cover the Doubler Ring area. You can still seal the Doubler Ring, nutplates and their rivets, but it's a mess and then you have to clean your squeezer before the sealant cures. Believe me I know because I did it.
Art Pennanen