I had the same problem with the EDF-50s, then I found this How To article: http://www.aeromicro.com/DennisDeFevere_EDF50_Rotor.htm
After I balanced the rotors, no rattle. Another great How-To article on these fans is about inlet & exhaust mods that increase thrust.
I found it a bear to make the inlet ring & exhaust cones from foam-- but AeroMicro will soon offer a vacuum formed kit of these that weighs almost nothing.
Got any pics of your A-10 with all the gear installed?