Long explanations are good
Well I can only tell form my experience.
Keir could never lie in his bed for 20 minutes before nap, for sleep he has to be out in 5 minutes or it will be scream later.
Hmhm, but given that he was out faster for afternoon nap, so why dont you try put him in bed,when he usually falls asleep, gives him a bit more real A time and then you get real nap time in bed and then maybe can stretch it better.
Take it as from someone, whose LO has 1 and 2 naps days when needed.
Depending on wakeup time in the morning.