When Simon is barking maybe you can distract him with a loud noise of your own. Once he stops the barking give him praise and offer a small treat maybe? Maybe too you can began to anticipate when Simon will start to bark, distract him and do the praise and treat thingy too....
Is Simon getting anough exersize through the day? Maybe he just has stirred up energy he is trying to release. Also, I've heard that a special toy just for night time (sleep time) helps to relax them while being in their crate, etc.
Good luck.
