There are no rules of weapon length for K-con and there have been some pretty huge props in the past.
Are you worried about moving about?
I would suggest holding it in an upright position when walking through crowds so no one gets hurts.
Doors will be at least 7ft so you should be fine. I've never measured a door height but I know they are taller than 7ft if not at it.
But if you want to be safe, even though there are no rules stating size of props, I would talk to one of the head Yojimbo.
However, as long as it doesn't cause any danger, you should be fine.