I have only competed a few times, and I do this, too. I am the harshest critic when it comes to what I turn in. I love talking to all the "looky loos" that walk around at competitions, because I met guys that were really friendly by once being that guy that walked around and observed. People always ask how I think I will do, and I always say, "Well, I did the best I could today, but it is up to the judges now." A little modesty goes a long way. I wouldn't call it sandbagging, I'd call it keeping myself in check.
Matt - 18.5" WSM; UDS; DigiQ DX2; Commercial Series Gasser; Maverick; Some Other Crap, Too!