How much is a little?
Using a dial indicator measure how much axle end play there is.I believe Ford specs out something like .030" as max.If the end play is in the acceptable range shim the caliper bracket to keep it off the rotor.
If the end play is excessive then it's time to install a TracLock rebuild kit to get the clutch pack stack height back into spec,which in turn will tighten up the axle end play.I like to increase my stack height to the tight side so I have less than .005" axle end play,even if I have to lightly tap the cross pin into place.