Steve, thank you very much for response. My portlights are from bronze
and are already cast (in Hungary, 750 euro per 12 pcs, but glazing and
polishing is on my side). I am thinking of installing them in outer
sheet metal sealing them with sikaflex and weld a bit oversized tube of
steel to the inside , long enough to pass through the thickness of the
hull. This solution seems it will work, however being in the boat one
will have a porthole in 4 inches deep well. Thanks once again-Przem