I could have written that post as well...

The thing that I found is being consistant. It used to drive me INSANE - every time we caught up with my family he would go insane - wee everywhere, throw things etc. My family used to take over and say things like your family. I put my foot down (in front of DS) and made sure people (including DS) knew that I was in charge of disciplining him. Once he knew the rules out are the same as home, things have settled down.

It sounds like you are stressed and I guess he is picking up on that and milking it for all its worth. Kids love consistancy - let him know that he is safe and secure wherever he is!

HTH