As long as you cut the steerer at the right spot and do so nice and straight across the real possibility of damage is to paint when the saw slips or goes through unrestrained. I suggest a beer can (pour the beer in a glass for after the cutting) wrapped around the top tube over some padding and taped in place to act as a guard. But seeing how easy it is to remove the fork one wonders why the risk to saw the steerer in the frame. Andy.