Downgrade without wiping data

[darkzero1125]

im on latest may patch, can i downgrade to april without wiping my data?

 

[cherryb8844]

im on latest may patch, can i downgrade to april without wiping my data?

Accept you are on stock. ?

 

[meltbanana]

im on latest may patch, can i downgrade to april without wiping my data?

yes, you can, but I did exactly the opposite and upgraded to the latest oreo beta after extracting the images with payload_dumper.py but system.img can't be flashed due to a "sparse image magic error" (sparsecrclist.txt missing?).
however now the battery life is amazing and the device runs pretty smooth though I'm still on oreo 8.0.
therefor I edited the flash_all.bat script from tissot_images_V9.5.11.0.ODHMIFA_8.0.
edit: prepared a download for lazy people which includes even a (magisk) patched_boot.img (I suggest to use fastboot boot patched_boot.img):
https://mega.nz/#!7WARiKaS!bEEUJzxxR2QtbqpVK5C0aUW3i2wrFIrnL7zZ3dn3Ghw