I think I could easily get 20 lbs of grain in my 10 gallon cooler, and a keggle is almost 15 gallons, so you should be able to go up to 30 lbs, I'd think.
Crap... Guess I'm just gonna have to back her down to 1qt/gallon.. 10 gallons of a big IPA with a 34# grain bill going on here.. Thanks for the help Guys... That blingmann link rocks..