For lurkers who may not know, NFP is used by Catholic couples to regulate the spacing of children. When NFP is used, it is used at infertile periods when the couple may engage in sexual intercourse without the result of conception.
The intention of the couple using NFP is to avoid conception, which is why intercourse takes place during infertile periods.
Perhaps you forgot "with GRAVE reason" for doing so, Sink.
BTW, I also noticed your little slip-up on "method is secondary."
Chemical/mechanical contraception is intrinsically evil. Per se, utilization is a grave sin.
As a Deacon of the Church, you ought to have known that.