I was also wondering about using OPK's for O+12? So far I've only used them to see how my Shettle timing was coming along...but I wonder if they could also be useful in O+12?
If you get a +OPK and it takes 36 hrs to O then bd 12 hrs past that at 48 hrs after +OPK = O+12?
or
do I also have to factor in the extra hours it takes from the LH surge to start until it shows on the pee stick? How many hours? 4-6 hrs? = 36 hrs to O + 6 hrs for it to show up in the urine + 6 hrs past that = 48 hrs after OPK = O+12?