I have been having great results pitching a single smackpack into my 13 gallon batches fermenting in my sanke fermenters. I usually buy a fresh pack right before i brew,smack it then pitch it when i'm done,active fermentation by morning in most cases. I try to cool wort to about 74 degrees and keep it in my basement where it cools to 67 or so. That couple extra degrees to start helps it get going strong.