I'm not sure that eye position indicators would have the same benefit in a light 'plane as a larger one. Though I'm not a large 'plane pilot, I expect that the light 'plane has more airframe (usually the engine cowl) in the pilot's view by which to judge attitude. A few types I have flown have poor visual cues out front of the windshield, so do require better awareness, I don't know if pre-established eye position would help that.