Having previously used hand warmers for zeroing, I read on the SD about using foil tape on the target, giving an inverted image. This worked but I thought if I used black paper it might give a better contrast between the cold foil and the paper. I found this chalk board paper on clearance sale at Tesco, £1 for 8 meters and its black printed onto white, not quite "shoot and see" but you will see the hole through a spotting scope. It might be worth a look if you get a chance.
