Hardcore gamers love expert mode because it provides them with such a challenge...but no matter how good you are at aiming, I don't recommend trying out this advanced level -especially if you ever have any ladies visit your home.
Having just read the excellent "Packing for Mars", I note that astronauts have to do exactly that... the toilets have a 4" hole, and they get to practice with a camera mounted in the bowl. Space is not for the faint of heart.