I told the rep at the service center the Sabre command to add the LP number.
FFLP(your number)/US-1.1
(the 1.1 was important, the agent tried her normal way without success).

I also had a gate agent update the record too. It was important for them to remove the
USAir dividend miles number 1st if it's present.

BUT it only seemed to work if it was done before the flight was taken. Changes after the flight is closed out (e.g. at arrival or later) seem not to work ... which makes sense to me.

I don't believe any US miles have posted yet since we just retook the LP creditted flights recently and then sent all the documentation to LatinPass, so it's still early for us.