Basically, I would start out with deciding on an approach within this 451. If you intend to play on the break, channeling the play through the middle and lauch direct balls into channels down the flanks, then its best to sit a litlel deeper and soak up pressure. Here, the fullbacks wont need to be that attacking as when lauching these direct attacks, they will not get up into the attack quick enough anyway. If you intend to play a control based approach trying to drag the opposition out of position, then why not use more width and exploit the flanks. Here, the fullbacks will be more attacking whilst the central Mcs will hold up the ball. You can actually use both approaches within the same Strategy. Balanced-Counter and then eiethr "play more narrow, drop deeper and pass into space" or " Play wider, exploit the flanks, push up and Retain possession"
As you see, its all about the style of play you want to use. Use the settings provided by the TC and only tweak( if wanting to) the wide play of the fullbacks, not anything else.