Mine are 800mm or 31.5" and I am 2.00m or 6'7" tall. they were originally higher but I found this impractical and cut them down a little bit. It was about 28 years ago now so I cannot recall
why they were impractical and it may have been because I considered the intermediate wire to far above the deck
The wires used were originally the 1/8" stuff with a plastic cover, which UV'd and fell off and I replaced them with 1/4" wires about six years ago as I tend to depend upon them more now that I am getting older.
I had my staunchens made from 1" SS tube with welded in ferrules as I did not like the flimsy looking things available from chandleries. The slip over solid pins which are welded to triangular 1/4" x 2" on a side plate doubler triangles welded onto the 1/8" deck plates. If I was doing the job again I would make these bigger as, whilst welded on above frames, they still flex the deck plates slightly.
The low single
line arrangements one buys from chandleries are token devices and whilst they may provide a hand hold are not trustworthy for life saving purposes.