Yeah, before I got the stir plate mine would foam up pretty good, but the stirring motion keeps the krausen down (for everything but my 3068 starter). I can generally fit a full 2L in a 2L flask with the stir plate without a problem since my 2L mark is at the bottom of the upwards curve. However, I also generally boil in a separate pot and pour into the sanitized flask once its cooled, not sure if I would try to boil 2L of wort in a 2L flask without some fermcap.