Does most of his scoring come from his guards? If it does, and they have 50ish PE, they are often inclined to take a lot of medium range jumpshots. If you set your 2-3 defense at -5, they will make a lot of those medium ranged jumpshots. I would be more inclined to play a team like that at 3-2 (-5) or if forced by personnel to play a 2-3, push it out to -3 or -4