As to your prospective bumps, make sure you hit a lobby agent first at your outbound airport to add yourself to that VDB list for your return flights as you want to be on the VDB list as soon as possible as even if return flights are not oversold at that point, anything in terms of iirops can happen while your flying and if there are enough volunteers by the time you land, you're hosed (and I say flights as if your first return leg is not oversold but your second return leg is you're already on the list
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