I ended up using SCS200. I had some onboard, it was suitable for the purpose. There are a number of silicones formulations that will stick to both acrylic and aluminum, but in every case the surface prep is critical, especially for aluminum.
As we disassembled and cleaned out hatch frame, the failure was obviously at the silicone/Al bond because there was a lot of debris of older sealant remaining behind. The surface prep for the last repair was just not good enough.
Once ALL of the old sealant has been removed, and the surface solvent wiped, the aluminum should be wire brushed to remove all oxidation and old sealant. Then wipe it again to be sure the surface is clean of dust. Cover with silicone sealant right away, before oxidation can significantly change the surface of the metal.
The surface of the lens should be throughly cleaned, and then wiped with isopropyl alcohol, then do not touch the sealing surface with bare fingers. Skin oil can reduce adhesion on the smooth plastic surface.
I avoid using solvents that can attack acrylic like toluene, MEK, and acetone. The risk of damage to the unsealed part of the lens is too high.
There wasn't anything unusual about the Goiot hatches. Things went very much as I expected. Hopefully, nothing to worry about there for years....
St. Michaels, MD, USA