I'd also pay to select seats in advance and take an aisle in rows 16 or 27 (26 if you don't mind the center section). These are exit rows and feature more legroom. More importantly, the tray tables are in the armrest so you won't be one of the unlucky ones to have someone spill under the armrest or raise it when you'd prefer a bit of a barrier. Like I said, I'd also try for day-of upgrades to WT+, since I've heard these sometimes go cheap (but check the proactive upgrade cost tracking thread for more details).