Originally Posted by
draver
I have had some success by trapping the unit with the window shade against the lower sill. Of course it all depends on the design.
That won't work for OP though as 787 does not have window shade right? (never been on one). Suction cup is probably the easiest but I think if a flight attendant sees it, he/she might ask you to take it down as it could become dangerous in a turbulence (flying object launch toward your head similar to mounting on a windshield of cars).