Sorry I'm not sure how to explain it further. If you put a load on the brummel/fixed eye end and it tensions the line inside the bury, you whoopie is made backwards. If it loads the outside line causing it to constrict on the bury, you did it right.
Tapers and milking the bury has nothing to do with your the whoopie slipping. Taper and milking only apply to the fixed eye.