adding decal to a rigged character from mixamo

Hello i'm adding a tattoo to an arm which work good but when i parent it (with  armature deform)  the armature the decal goes up and away and grow , the armature came from mixamo with a 0.01 scale where the model part are at 1.0 scale 

i presume that the scale is the problem but havent been able to fix it by myself maybe someone here have an idea

thanks