After several ales, for my first Lager I will brew an Oktoberfest. Planning a 5.5 gallon.(fermentor) batch with about 13 lbs Grain, so maybe 6%+ ABV. At the beer store, I picked up one package of Wyeast 2633, but the package says "100 Billion Cells", and I am thinking that is dramatically underpitching. Am I OK with just a single package, or should I pick up one (or more?) additionals? I expect to ferment at around 50 F. I do know that overpitching is not harmful, but the store is not near by. My ales have been fine with a single package of (whatever), but I am led to believe Lagers need significantly more? A recipe similar to mine in Palmer's book calls for 465 Billion. Thanks for your thought and consideration.