I'm guessing Koreans are really short! Both the door and center armrest are way t0o low, even with the seat all the way down. If I slouch to one side or the other, it is comfortable to use - for like two minutes!
I've been tempted to build up both but haven't. Good for you for doing it. I was thinking about a design for something easily removable, that uses the armrest cubby a female for a male protrusion.
I've even looked into a handle above the door (my trim doesn't have one on the driver's side) as something to help with this deficiency. And as has been the case for the last twenty years with raised greenhouses on cars, the open window is too high to comfortably use as an armrest for long.
2018 Kia LX HEV Metal Stream with Advanced Tech