Alv, I would go in at 8:30 and check every 10 or 15 minutes.
By the way, last year, they estimated at 11 AM the number of no-shows, so made them available then. I have not asked what they are doing this year, but I'd guess 11 AM is the best time.
...maybe you could find out when you are there and report back.
I walked in on June 7th (a Friday) looking for a permit for Saturday. It was about 10:45, and there were 3 slots left. At that point in time I was the only one seeking a walk-in permit. The ranger asked me to come back at 11 - just in case - which I did. He jokingly said that if he had issued one at 10:50 then it would be just his luck that 5 people would have walked in at 10:55. So - my WAG is that it may depend upon the day of the week, the weather forecast, the experience of the ranger, the number of slots left, etc as to whether you can get permits for the following day prior to 11. I wanted one before "high" season, so demand would tend to lower, but it was a low-snow year, and it was a Friday.
