Had trouble finding info on how to open the ISDT C4, until I finally somehow found this video: https://www.youtube.com/watch?v=K6x7sLFgUHc
There's a total of 6 screws. 2 in the battery bay, and 4 under the screen:
Maybe putting this here, will make it easier for google...
Some other cool mods/hacks I found on thingiverse and might try myself at some point: