The walk-in alternative may not be necessary. As the date nears, people cancel. The nice people that cancel take the time and effort to notify the Permit Office (or now Recreation.gov) so others can use their permit. I lucked out this way several times even on an August weekend. The odds are good that someone nice will cancel on your June Wednesday and turn in their permits.
Remember, as your hike date approaches, you're only competing for cancellations with people who are flexible and ready to go on short notice. So keep checking Recreation.gov right up to the last minute. You might be surprised.
