to me, I think it's best to display the model with the hood/doors whatever closed at first, when it looks like the judges are making the rounds, open everything up that opens. usually the judges will walk around looking at all the models before actual judging begins.
I figure if all is closed etc. during the casual observation, they get a look at it in one 'light', then when the judging begins, they see it in another 'light' with everything open and showing.
I could be completely wrong, but it seems to be what I have noticed at the shows I have been to.