Depends on what you think your luck is like. Personally, I would normally keep ALL of a clutch if the sex ratio is half-way decent. And btw, don't cut yourself short on males. A lot of people will do that, get slapped REAL hard by Murphy's Law, and then be sunk with the project. I don't know how many people have purchased 1.4 of some project animals from me, and I just shake my head at their lack of realistic foresight. I also don't know how many people over the years that have contacted me in a panic during the breeding season because they lost their only male and needed one RIGHT NOW for a project they were working on.
Hope for the best, but plan for the worst.
Quite frankly, unless I have three males for breeding stock (no matter how many females), I feel like I'm too close to the edge of failure on playing the odds to make it worthwhile pursuing.