I know you're all talking Boeing, but the Airbus FCOM says to expect rudder trim to reside between 2.3 units Left and 1.0 units Right in the cruise. I rarely see it, if ever, sitting to the right. It's nearly always left trim.
I mention it because the cargo doors are on the right side of the A320 too so you wouldn't expect left rudder trim if this theory was true.