If its soft boot riding then set him up as duck footed, +15 front -15 back is 'normal' over here. Ensure the boots have a good upturn at the toes and heels (if you have any choice of boots at all), and put risers on, ex. Palmer Power Link System Standard Lifters.
This should cut down on toe drop.
As to board width, due to the fact hes got - lets not beat about the bush here - big feet, its all in proportion to the width of the board. As most, if not all, turning is done from the knees down (well over here it is), with the emphasis on foot steering, it won't create a major cause for concern having him on a wide board.
(having just read the original question that doesn't really help). I beleive size 16 is about 32.5 mondo, and most manufacturers stop at size 15.