I don't know if there is anything you could change to make it different, there are no "no offset" natives for set object coordinates or get object coordinates. I'm assuming you're using get object coordinates for the left side info, I was expecting those coordinates to be exactly the same as what goes in an objects.ini but I guess they aren't. Everything is perfect except the height, it's not a static difference either, the big barges were about 15 too high, and those tanks I edited in were about 9 too high.
You might be able to come up with a formula using the model dimensions but I think that's making things harder than they need to be. It's simple enough to change the one native in the map mod loader.