I have found a breakthrough about remembering the 4th tone mnemonic - the bathroom. I have struggled with it because the mnemonic stories are often like fever dreams - insanely crazy. Therefore bathroom often got confused with the main room and basement (outside is fine). Especially in such unusual locations like barn or chapel. Then I found a solution:
Imagine the bathroom being on the second floor, upstairs, on the attic, anywhere higher in the building.
It helps a lot, try it yourself. Elevated location gives it great bonus to remembering