Your problem with the aluminum soda tabs (square tabs) is common to all detectorists and all different brand detectors. Most of todays soda tabs will ID as a 'nickel' to all calibrated ID detectors. Nothing we can do about it. The CZ has the tightest nickel window in the industry, yet, it'll still ID a lot of aluminum square tabs as 'nickel'.....................just............not as many tabs as other detectors. ...... Even with tabs 'notched out'...... they still ID (conductively) as a nickel......so the detector will give a good audio report. Nickels are a VERY difficult target to ID.....because they mimic the aluminum flip tabs.
And if you notch a certain window/conductivity of targets out.............you still run the high probability of that specific notched out target being in close physical proximity of another target.........causing the reading/ID to change/alter,,,,,,,,,,,,,,,to the point that the detector will audibly report a target.
OR.........dirt mineralization will conductively 'shift' the ID of the target AWAY from its 'notched out' window; and ....... once again...... the detector will report a target.
OR........the notched out target is tilted or on edge.......and...........once again........the detector will report the target.
These are some of the biggest reasons as to why I do not like to use the 'notch' feature. Under textbook/ideal conditions.......it works.