It's also when you start introducing traps (tunnel close to contact), tight turns, weaves etc which cause them to change their stride that you might start to encounter a less definite hit. Either on or off the equipment.
Also, be prepared to have contact decisions go against you. I can say that we get marked occassionally for a miss when I know she has run through ok, they are very difficult to judge and unless you have a perfect hit rate it can be difficult to tell.