1.25 gallons is a crap-ton to leave behind in the brew kettle. How are you draining it? If it's just a matter of the drain hole being too high up on the side of the kettle, maybe you could look into adding pickup tube. Basically, a pipe elbow on the inside of the drain that points to the bottom of the kettle. Because of the siphon effect, you end up draining all liquid down to the level of the bottom of the elbow.