I've got a compromise....
Test him 24 hours BEFORE the fight, and ALSO immediately AFTER the fight. That way, you will satisfy Pacquiao's concern about blood loss just before the fight and Mayweather's skepticism of Pacquiao being clean.
That is exactly what Pacquiao wanted....but Mayweather did not want that. Knowing full well that the Pacquiao camp would not except the conditions of test up to hours before the fight. Mind you, and I am sure I will be corrected if I am wrong, Pacquiao is the only box they have requested this for.