With the right luck, I think the all stages run could hit sub 20'30. I lost maybe 5-6 seconds in stage 2 by botching the start. In stage 4, nerves hit me and I was super cautious on the bridge but then I missed the jump pad in R4 which cost another good chunk of time.

S1 - 3'41"37 S2 - 4'44"53 S3 - 5'57"03 S4 - 6'15"30