big slice

[knackrs]

i have a mean slice, had all the usual..posture,alignment, in out swing etc,etc, still slicing. big time.
i have a theory to which i would appreciate feedback,...i am left handed when using one hand then i am right handed using two hands, could my problem be that my left hand is pulling the club through the downswing, if this is so is there a drill that someone can recommend to eliminate this

cheers

knackrs