As these guys have said if you get low in an AT and you are getting out of balance and this is pretty easy to do if you are really in a hurry doing a racetrack, there is a bit of form on the board to suggest you will run one tank bone dry and some machines have failed in this situation.
As turbomann said if you keep flicking between tanks and keeping a very close eye on things you will probanly be ok if you are caught out. And we all have or will be caught out at some stage.
If your Shadin is calibrated well and you know that for a fact, ie by regularly cross checking what the shadin says you have used by what your fuel bowser tell you have when you get home. Then you have another great tool to use to know how you are going. BUT remember you only really know whats left if you know exactly what you started with in the first place.
Another tip with those wings is to remember that if your refueling with a fast pump it does take a bit of time for the fuel to transfer out throught the holes in the ribs to the outer extremerties of the tank. If your groung guys are filling you to tabs, make sure they give you a second spurt or over fill the mark by at least an inch to alow the level to settle back to the mark. Every aeroplane/pump combo is different there and your ground crew will get to know it.
And in this day and age if you have a prang because you have flown below the reserves in your opps manual the insurers may come knocking!!