That's a biggish gap between O-3 and O though - does FF really say to do that? My reading of it, is that O, O-1, and O-2 are the better days overall, I quote: "For conception purposes, it is thus ideal to have intercourse during a three day fertile window which includes your ovulation day and the two previous days." That is O-2 not O-3? I'm not saying O-3 won't work, just that O-2 or O-1 may be better if you're only going to do 1 of them.

And also, from Fertility Friend, I quote "The most likely day for intercourse to result in conception according to the 1969 study was two days before ovulation. According to the 1995 study, the most likely day for intercourse to result in pregnancy was on the day of ovulation itself. Further studies have been done, however, to account for measurement error in both studies and to exclude early pregnancy losses from the Wilcox et al data set. With the corrected data, the most probable days for intercourse to result in pregnancy have been found to be one or two days before ovulation rather than the day of ovulation itself (Stanford et al 2002)."

Thats the premise most gals work off round here, 0-3, 0 and 0 +1. Most of use (or used) FF.

You also have to factor in the lifespan of the egg.

Your best chance is timing very close to O (just in case none of your partners little swimmers are lying in wait from days before) so I just wouldn't skip the day the above method tells you to. Otherwise, it's a good plan.