From my experience, if you want to make sure you are ahead of PLT/GLD in the new flight, pay the $50 same-day fee. Sometimes AC agents can clear you WITHOUT the fee and hand you a BP. This is because they see you are first on the SB list and a few seats are available. So they figure you will clear SB anyhow. However, the GA will still treat you as a SB, and clear everyone else before you.