If you are in a program (or even a custom program of your own) that is set to "knock out pulltabs", you have to keep this in mind: "pulltabs" can come in many different sizes and shapes. When you start include bent/folded-over ones, chopped ones, different sizes from different brands of soda, etc.., you find that there is really never a 100% "pulltab zone" on any TID detector. There is no one particular coordinate on any TID detectors, that is always "pulltabs", verses other low conductors. If you really want to be gauranteed to find zero pull-tabs, then you will need to knock out
all low conductors, and only dig high conductors. But then of course, you will miss gold rings.
If tabs in your hunt site are fairly consisitent in size & shape, then you can notch out *just* those types, and perhaps be left with much less tabs to dig. In that case, you would only find tabs that are outside of the perameters/settings of what you have notched out. But you will still dig foil wads, bent up tabs, and anything that is outside your disc. pattern, and you will still miss *some* gold rings that fell into your notch patterns (that mimicked the exact reading of the notched out tabs).
If anyone tells you that they can tell aluminum verses gold, quickly take them out to the nearest blighted inner city junky park, and see how long they stick by their claims