gender selection

i have three girls and would love to have a boy. I have read lall the books; Shettles seems to be the most popular one. However this is my dilemma. TCOYF says you may have your most fertile cm or peak day one or two days before ovulation, which I believe I do. I think I ovulate a day or two after last day of peak CM. (Still trying to determine exact time, and hopefully will this month with a combination of methods.) However, if ovulation occurs 2 days after peak eggwhite cm, and Shettle advises to have sex on day of ovulation or one day before for a boy, yet everyone concurs that ideal conditions for male sperm especially are peak eggwhite cm, then what i am i to do? If I wait till ovualtion day, then i won'tt have peak cm. If I have sex on peak day, then this could be 24 or 48 hours before ovulation, which may produce a girl, according to shettles. Would like to hear from others on what did and did not work.