I've been talking to folks who have shipped lives for years. Two things appear to be important, airport to airport is one. If you can take them to the PO at the airport and the recipient pick them at their airport.
Not all local PO offices were created equally. One friend has found that taking her birds to a different PO location has resulted in better results when she ships her birds.
Sometimes PO will not let receiver pick up the birds from the airport...as in my case.
many times I get shipped birds all over the country, they will go from a small country town, deliver to major city, then fly to another major city like St Louis and from there, truck them all the way up to my town.
I think it all depends on the post office and what they are willing to do.