no, most people that do that will likely be turned away because it's a hassle to rebalance pools, re distribute the pot, and add more people in when you want to get a tournament running. Not to mention we might start before 6. Exceptions will be made if there's no possible way that you can make it until 6, but if 20 or 30 people pull that card, they'll probably be denied. I don't want anything to be delayed for longer than necessary.
You could enter just singles if you still arrive at 12:00 for registration, but in that case you might as well do doubles because you'd just be waiting for 6 hours.