All things to consider , he says the original install was 92 and from the way he described it it sounds like a Otis welded head cylinder and has evac ports so it should be double bottomed . The building is a car park and as far as I know it would not of been a provision for extra floor . However I didn't even consider it may not have a stop ring or stop ring removed . I presumed they either ordered wrong size piston or the building was shortened between ordering materials and construction . I have had the opposite a few years ago where they extended a building by 4 foot after ordering the elevator ! . Now how to tell if he has a stop ring ? Hang the car near the top and pull the piston as I he was going to replace it see if he can pull it up enough to see or run something down to see I he can feel one ? I suppose that would give him an idea of where it was too and how much he needs to add ?