It really depends on the club to stiff with a 3 iron will result in pushed shots and miss hits or straight weak shots. where to stiff with a 7 iron wont make much of a difference for instance you could compare to identical 7 irons heads one with a reg flex and one with a x and find the x to go lower stay on target and have about the same distance,the reg would go higher just as straight sometimes and then randomnly seems to go 8 yards farther to the left. This is because it kicks later and sometimes just jumps. What happens with the longer clubs is their harder to square up and way so a reg fl