I think the aim is for approx 1:1 ratio between REM and deep.
If you sleep for 8 hours then the optimal time in REM is 1.5 to 2 hours. And the optimal amount for deep sleep is 1 to 2 hours.
To decrease REM and increase Deep-
Go to bed on time.
Relax, try calming activities to prepare for sleep.
Avoid or limit caffeine and alcohol.
Exercise but not too intense or late in day.
Last night after 2 loops of Genesis I got almost 2 & 1/2 hours of REM and not quite an hour of deep.
So, no more than one loop for me, especially at night.