Nonrev on the Delta Shuttle?

Has anyone done this?

When you check loads, it shows lots of seats but when you look at the airport standby list, it shows only 2 open seats.
I know it is mostly walk-up.
We plan to fly on a Saturday so that would help since there won't be many business folks.

Yup it's usually upgrades and platinum members. But I know the feeling, exactly where do 50+ seats go in 4 hours??????? Well for me it was members of the University of Texas marching band; they missed their flight.