The 4.5h core allows all SWS needs to be met even during adaptation, since monophasic sleepers typically gain all the required SWS by the middle of the night, after their 3rd sleep cycle. The ideal core placement is around around midnight, for a good balance of REM and SWS pressures. It is recommended for the first nap to be placed the middle of the REM peak of 6-9AM, allowing high quality REM sleep for the nap. The second nap on E2 may only contain light sleep rather than REM sleep, especially if this nap is late into the afternoon (e.g, 4 PM onward).
