What you have to remember with a puffer, the coal bunkers, boiler and engine were all below the wheelhouse and engine casing, so with the ship unladen, it had a definite stern low attitude, with the bow sticking up at an awkward angle.
If the hold is shown full of coal, as many people do, the waterline should be just below the freeing ports, or even sometimes with the main deck slightly awash. The ship pivots about a point just below the wheelhouse, and would very rarely, if ever, sit at the nice, neat, high out of the water and horizontal level most modellers have their boats at.
It is for that reason most of the anti fouling was from just below the top rubbing strake, not further down. As in the attached pic of my build from many years ago.
This was the old style of hull built from curved plates, unlike the later Vic series which used mainly flat plates, like a TID tug.
John