I know they reccomend filling your spool to within an eighth of an inch from the top, however why exactly is this? I've been using baitcasters for years and sometimes i cast better with less line. If its a 6.3 to 1 reel u still get 6 turns to 1 rotation of the handle. Is the main reason it is suppose to cast further with more line?? I always put a backer on all my reels too with some cheap line so i can change out often and with the price of line you have to. It sounds like a dumb question, but I know somw guys who almost overfil and some who barely put any line on at all??? .............what do you like to do?