The fact that the bottom paint is high above the scuppers doesn't necessarily mean it was always sitting like that. It can mean that over time, the water line got painted higher as the hull sat lower. You can't tell foe sure without knowing what it was years ago.
I would expect the scuppers to be above the water line in general as part of the design but perhaps not with two full tanks.
Try looking for photos of other 228s. You might be able to see how they sit.
Your situation makes me thing again about the physics so I am going to ramble on for a while.
If your hull were a flat bottomed box, the depth it sat in the water is determined by the displacement and of course the weight of everything added up. Lets say your boat was square and flat and sat 10 inches into the water.
Lets also assume it weighed 4,000 pounds with whatever it had in it plus the weight of the hull, motors, mechanicals etc
That tells me that each inch of draft represents 400 pounds of displacement. If you were to add 125 gallons of gas, you would add about 750 pounds of addition displacement and that would lower the hull a tad under 2 inches.
Of course, you hull is not square or flat and your load is not evenly distributed but I feel that my math may still give an indication of change in draft. Yes in a real hull more weight would be distributed aft but at the same time as the stern dips the surface that contacts the water is 'flatter' than the forward areas where the dead rise is more aggressive.
I need a model boat and a tank of water to test my theory
Or I could get a degree in marine engineering.... I will look for a model boat!