An article from '08:
WGCDR Smith: "A good majority of our FSP students come to us with less than five hours total flying time. While we prefer them to have done some flying so that we can be sure this is what they want to do, sometimes having more experience can impact them, but we keep an open mind".
http://www.******************/files/B...g%20School.pdf, p. 49
Having read that though, the majority of guys I know who scored extremely well (stanine 8-9) had between 10 and 20 hours behind the controls. Read in to that what you will!