I did a 2 Gallon, full volume - no sparge, AG Oatmeal Stout this weekend with 4.375lb of grain, and 3.5 gallons strike water.
My 4 gallon pot was full to be sure, but it held.
Wrapped it in a towel, a sweater, and my winter jacket and only lost 2-3 degrees over 60 minutes.
Not too Shabby.
Fermenter 1 - Vienna /Saaz SMaSH
Fermenter 2 - Dry as a bone
Drinking - various craft brews, Tiny Bottom PA
Beer styles I'm trying to nail down: APA, Porter, Mild, Amber, & Something Yellow and Fizzy.