Answering the original question the 737-800 that I flew for two years in 189 Y config had no trim problems and certainly didn,t require any special seat row consideration other than a reasonable spead throughout.A very flexible,versatile commmercial aeroplane if not a firm pilots favourite.I position regularly with BA on earlier series 737 and note they sometimes block the front rows for "trim reasons"???.I,ve had the pleasure I believe of working with "Tight slot" as my cabin manager on both the 738 and other aircraft, a most excellent person and erudite P.A. orator, well qualified to speak on the subject.