I see a lot of homebrewers advocating 4 and 5L flasks for lagers. But, 4 and 5L flasks aren't really necessary for a traditional 1.048 pils, as far as I see from using my yeast calculator. I can start with a 1L starter, step it up to a 1.5L starter, and end up with 397 billion yeast cells. Isn't a 2L flask adequate for this task?