I think the sweet spot is larger than you suggest, Neuro, if ampakines have not caused sleep disturbance in the trials so far.
The fundamental disturbance in sleep apnea is drop in oxygen level which causes awakening by an enhancing drive for air, as if you were under water too long. This occurs repeatedly, many times during the night, preventing quality or restorative sleep from occuring during night. Hence the patients with sleep apnea are very sleep deprived and will tend to fall asleep during inappropriate times and in inappropriate places throughout the day.
This is also why a simple day time sleep tendency scoring system can be an accurate indicator of the severity of sleep apnea. This could yield an easy indicator validating sleep apnea efficacy, without a complex expensive overnight sleep study.
If the ampakines can avoid the oxygen drop by increasing the tonic stimulation of the basal breathing centers, the arousal mechanism that would trigger awakening, would never come into play, and restorative or high quality sleep would follow.