I’m as close to an avid desciple of John Deakin as you can get, but as he cautions, you have to read and THINK aboyut his comments before you follow them blindly in your aricraft.
I can only speak for the SR22 - SR20 drivers, this may or may not apply. I also mus tnote that this is just my opinion.
The '22 is very sensitive to unbalanced fuel loading. The POH calls for (reguires?) that the fuel load not be unbalanced by more than 10 gallons. My experience is that I change tanks more often than require to keep the fuel levels very close. Add to this that if a wing is low (typical if the fuel load is imbalanced) or the aircraft is at all uncoordinated the fuel gauges read very inaccurately. After assuming a straight and level, coordinated attitude for a few minutes everything balances out and the gauges look very accurate. I’ve seen the gauge vary by as much as 5 gallons due to the airplanes attitude. I assume using the last bit of fuel ‘unuseable’ would be difficult unless you are very straight and level.
The problem is that as soon as the fuel load becomes inbalanced, the aircraft flies quite a bit heavy wing low. Therefore to suck out the last remaing fuel, the ‘full’ tank would also have to be very low. Not something that Deakin recommends.
I’d definately recommend running (or draining a tank) and filling it to see how much it really holds, and maybe calilbrate a dipstick along the way.
I also have no problem with his advice that there is nothing wrong with running a tank dry - just his method would not work well in the SR22.
Finally, if I ran a tank dry with my wife inthe plane, I would probably hope that I couldn’t restart it, because if we survived, she’d kill me once we got on the ground.
Know your airplane, know yourself and know your passengers.