On the rare occasion that I ride in the back, I just wedge my knees in to make it impossible to recline. Problem solved. Honestly, on most planes in Y (not in exit rows) my knees are naturally jammed into the seat in front of me whether I actually try to do so or not. After a few tries the offender always gives up. Sometimes there's a nasty glare involved, but no big deal. People see how big I am and then lose any desire they had for a confrontation.
