The whole Goff Nautilus is a diving plane. The small "Diving planes" in the lateral keel chines could be thought of as trim tabs like those found on the rudder or elevator of an airplane. They point the undercambered airfoil Nautilus relative to the water flow thus changing the angle of attack (AOA) causing lift (dive) or steady level cruising. About 2 deg negative angle of attack (relative to the undercambered airfoil lateral keel chines - not the sub) in the Nautilus would be used for cruising underwater. At around negative 2 deg angle of attack the Nautilus would NOT rise or sink AT ALL (not considering the wheelhouse or salon effect). This angle of attack is what matters here. It is the chord line of the airfoil (leading edge of the curve to trailing edge of the curve) relative to the direction of water flow. The lateral keel chines and hull are the airfoil. So a line must be drawn from the bow (from around first serration) to the stern (just before the prop) and this is the chord line. The flow of water relative to this chord line is the angle of attack. This angle of attack must be NEGATIVE so that the Goff Nautilus is not sucked down. This means that the Goff Nautilus must cruise with this CHORD LINE pointing 2 degrees UP. This has nothing to do with the deck being level or not - it is the chord line of the lateral keel chine's airfoil that matters. This happens to be with the deck just about level on the plans (don't know on the different models) and could be checked with a protractor. Goff's is a carefully thought out design.
Naturally, things get more complicated when you consider that the models out there all have gigantic, squared off, paddlewheeler-like salon housings masking the water flow on the entire rear half of the lateral keel chines - destroying the hydrodynamics. This would disturb the water flow over the rear of the inverted airfoil moving the airfoil center of pressure forward and making the sub more unstable. They don't stick out into the water stream that far on the plans, or the 11 ft! I'm still trying to figure out how to sink mine into the sub hull some. Err on the flush and rounded edged, streamlined side with the salon pods - like on the plans!
Jules Verne's Nautilus as described in the book as I recall used only ONE pair of diving surfaces at the CG. This provided downward lift and "sucked" the sub downward. Some very early sub designs had only one set of diving planes. Goff's Nautilus does the same only streched out along the entire sides of the sub. These could be thought of as extremely low aspect ratio wings allowing function at larger AOA than normal. Not only that, but the serrations act as turbulators on the leading edge and may allow still larger AOA as well.
What is different about the Goff Nautilus is that it not only acts as an inverted airfoil - but an UNDERCAMBERED inverted airfoil. This has more lift (at our speeds). This makes it very efficient at diving - AT A POSITIVE ANGLE OF ATTACK ONLY. Also this type of airfoil requires more care in the placement of the CG due to a greater pitching moment. This can be compensated for by the stern diving planes somewhat IF they are allowed to work by having realistically sized, streamlined, authentic salon housings.
The water hitting under the bow curve does push up on the front of the sub. This happens when at a negative AOA, and this in part, is why the airfoil has no lift at negative AOA (no dive). You could think of them as diving planes pointed up against the downward tendency of the overall airfoil if you want. How do you adjust these "diving planes" ? By trimming the whole sub up or down. I think its much simpler to consider the whole sub as an inverted curved wing and just trim it (point it) up or down, as needed for steady cruising under water.
Bottom line is if you use curved up lateral keel chines you need to carefully set the CG (due to pitching moment), and trim with the bow slightly up and the deck more or less level underwater. If you use straight chines almost none of this occurs, but it takes longer to submerge when moving.
This Nautilus would have been great for getting under water quickly to attack ships. Trim the nose down, ramming speed, and its under MUCH faster than ballast tanks alone could do. When at proper depth underwater trim to around negative 2 deg AOA to stop the dive, and go to ramming speed. Have you noticed the GIANT, PROMINENT angle of attack (level) gauge in the wheel house?