Imagine this: You place your model on the table and then someone else places a model on the table next to yours. Unfortunately for you the other model is clearly better than yours. But the other model is being entered by a proxy which disqualifies it from competition.
Now everybody who is at the show can see that your model is inferior. But when the awards are presented you get first place and the other model gets nothing because it was entered by a proxy. And since you were standing there near your model when the awards were given out you heard all the little comments like "Seriously?" or "You're kidding me!" or "He must be friends with the judges." Are you really gonna be ok with that?
And how are you going to react when someone walks up to you and says: "You realize the other model deserved to win, right? Anyway, congrats."
Heck, this is almost as cheesy as getting a first place simply because your model was the only one in its category. If you want a competitive edge build better models.