Many character staves will cast the string to one side slightly despite your best efforts to correct it. You can use the side with a bias to it as the arrow past, thus reducing the amount the arrow has to paradox around. This will minimise problems with wide staves. On a historial note, Mary Rose bow X-13 has a max width of of 42mm so is quite wide and goes over the 3/8ths 'rule'. Perfect design for the fruit and nut society, of which I am a fully paid up member!