Usually historical competition pieces aren't worn in the halls either. They might be worn to the green room from the wearer's room without too much cover-up but generally aren't wandering around all day.
Whether it's the rule for the masquerade or not the surprise factor is a major deal at CCs. Generally the really Wow stuff is saved for onstage and more maneuverable and comfortable outfits are worn during the day while you move around in panels, etc.
So give that some thought - it's pretty neat to surprise everyone, audience and judges.
Chair Costume-Con 16 (1998) St. Louis, Missouri, USA
founding president SLCG, chapter ICG
President of the ICG 2006-2009
2010 recipient ICG Lifetime Achievement Award
Annual Conventions: Costume-Con, Archon