HI,
I used preseed on the two cycles I conceived on this year - I am sure that you can't just put that down to using preseed but it does certainly help get those little fellas swimming (according to the literature!).
I will be using it this month in the hope for a for Christmas!

I think it would not be of any benefit to be using this four days before ovulation. I would use opk's to pinpoint expected ovulation and when you get a positive use the preseed. Doing this will have those little fellas up there waiting for the eggs entrance!
Wishing you all a for Christmas!