For Gullwing components, there are two options:

Currently, when trimming, the maximum body dimensions are considered. However, this often leaves only a very small heel solder area.

Why use the maximum dimensions instead of the minimum?

The paste opening already includes a reduction, which moves the solder paste further away from the body. 

When minimum body dimensions are used, the pad remains larger, allowing more solder paste to be deposited. This results in increased solder volume and a stronger heel solder joint.

Note: IPC’s concern is that 70% of the solder joint strength is in the heel of the gull-wing lead. When you trim the heel of the pad, you effectively remove heel solder and therefore reduce the heel solder joint strength.

This feature was added for customers that wanted to trim the pad to the 'Nominal Package Body' when the 'A1' dimension was 0.00. This was to avoid potential solder bridging under the component. 

However, IPC does not endorse pad trimming under the low profile component package. Their position is that no one has ever complained about solder bridging under low profile components. IPC recommends that you turn that feature off in 'Tools > Options > SMD Pad Stack Rules'. 

One of IPC's biggest complaints for component manufacturers that have robust tolerances on the 'L' dimension. Some 50 mil pitch SOICs L dimension is 0.40 - 1.27 mm. This makes a very sloppy pad length where the pads grow dramatically under the package. This was the cause for concern. 

However, todays metric pin pitch SOPs have a much more reasonable L dimension of 0.45 - 0.75. 

Also, if you use the mfr. recommended pattern, you'll notice that they trim the pads from under the package.