I've been playing with FCG since I read about it, and I believe that anything less than 25 mana sources is incorrect. The deck really needs the mana, since after all casting a Recuiter ensures you will never see another land for that game.

Of course you can hold unto a Matron or keep a Foothills in play for shuffling purposes, but that's generally not a good idea because that just means that you aren't losing, when you clearly want to be winning.

My build runs only 3 Skirk Prospectors -- only because my metagame has SO MANY scrubs that I felt an extra Sharpshooter was worth it, and it did help pull off the combo win faster.