Rich,
Cast -off has been on British guns for a long time, well over 100 years, But!...Many folks who think they have it figured out for themselves come up with excessive cast off, (Or on, depending.)
Mostly, if we get the drop right at nose of comb and heel , 1/8 -3/8 max in normally enough. Head erect shooting posture helps too.
As someone said up the page, too much of either and it'll bight you.
R.