I faced this exact same challenge in deciding upon a course of action for tomorrow's IAH routing. Because UA gives away nearly all of its domestic F seat inventory days in advance and holds little to nothing in reserve, IRROPS continues to be UA's Achilles' heel for me. I purchase a P fare, and still at times wind up flying in the back while an upgrader on a cheap Y fare flies in the front. Incidentally, can someone please tell me what happens with PQM in such a case? If I accept Y routing on a P fare, am I looking at 100% PQM or ??