3068 is the reason I bought a 6.5 gallon fermenter for 5 gallon batches.
It was literally pouring out the neck of a 6 gallon better bottle. I don't think an extra half gallon of space would have contained it, either. Next time maybe I'll rig up a three gallon bottle as a Burton union.
I use a make-shift blow-off tube by taking the cap and cup off the airlock. 1/2" ID hose fits perfectly on the stem. I then run that tubing into a plastic jug filled with water.