I wouldn’t do it, especially on purpose. Also, I wouldn’t let myself get into the situation accidentially!
I set my Garmin to do a warning to switch every 45 minutes, which is about every 8 gallons. (It doesen’t recycle when you shut down, but it’s not a problem…just change when it says, and you’ll never be out of balance.)
I purchased a dip stick from Sporty’s, and calibrated it. I’d be happy to pass along my calibrations, but would suggest doing it yourself. Also, I purchased two 6-gallon plastic gas containers from Wal-Mart and a gas siphon from Auto Shack to offload if necessary. (Someone suggested using cheesecloth as a filter when putting gas back into the plane, although I haven’t done it yet.
I think that this procedure will answer your needs, without introducing a major imbalance risk.
Doing some mental exercises for the upcoming SR20. What is your experience with unbalanced fuel. I know the SR22 has a limitation, but the POH of the 20 doesn’t mention any limitation. However the Wings Aloft training manual says “the SR20 is sensitive to fuel imbalances” suggesting to keep them within a quarter tank but with no other information.
Specifically if we have one tank full (28 usable) and the other to the tabs (13 usable) will it takeoff well? What’s your experience? This would be an easy way to fuel the plane if you knew you needed extra weight carrying capacity without having to rely on the gauges or a dip stick etc.