I though you had a 50/50 chance either way. Im not sure how to sway in one direction or the other. What does timing have to do with it?
I'm not sure exactly on all the methods, but for example male sperm are faster so if you bd close to ov then you could be more likely to get a boy, whereas female sperm are slower but live longer, so if you bd a few days before ov you could be more likely to get a girl.
There's are lots of other ideas and theories, certain possistions, diet etc.
Don't really think any work that well, but worth a try if you have a preference.
Also your chances are actually 51% 49% in favour of a boy as there are slightly more boys born each year than girls.