[caldrail]

The A5M was a very light aircraft,so yes,it's possible that the central fuselage served as a wing.Just like in happened with an F-15 of EAF.
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The A5M has a tube-like fuselage which gives low drag forwards but unless at a reasonable angle of attack very little lift if any, and even then, the curvature of the fuselage would allow air to flow around it thus much of the lift gained from pressure underneath would be lost. The F15, with a flat fuselage, is far better able to generate lift.

I did once claim to have gained some measure of lift in a Cessna during a steep turn from the fuselage side. Thats because the fuselage is more slab-sided on at 90 deg, and in any case, I did concede that the lift generated was very small. You might argue that my steep turn was actually a very flat chandelle. Well... It impressed the instructor!