that's one of my reason that I changed from 5 to 10. it looks 10 and 15 are most popular choices of bid directory owners.
My Voisd Bidding Directory of Directories has only 5 on the index as well - submissions should explode (fingers crossed) once it gets its PR4/PR5
I have the top 10 on the homepage of FoSee Bid for Position Directory But each of the 10 listed on the homepage gets 3 deeplinks listed on the homepage with their listing as well, not just in the details page. Tuleja.