I got a new PDF book I wanted to read just before my first train trip since Covid. I put Elipsa + cover in my computer bag, and discovered that it was quite stable on a definite slant. The first picture is the biggest stable angle, the second a medium angle. In both cases, that is valid as long as one doesn't use the stylus, but it supports the train's movements. I read very comfortably so for a few hours, since the table was holding the weight and the biggest angle was perfect for reading.
http://ipparis.fr/documents/elipsa_1.jpg
http://ipparis.fr/documents/elipsa_2.jpg