What setting should be enabled to help prevent failures while removing a face adjacent to a blend face when creating a shell?

Enabling the setting to add a shelf face at the tangent edge is important when creating a shell because it provides a smoother transition between the blend face and the adjacent surfaces. This helps maintain geometric integrity and ensures that the shell operation can be executed without errors.

When a face adjacent to a blend is removed, it can lead to complications such as discontinuities or undefined geometry if the transition isn't handled correctly. By adding a shelf face, you essentially create a stable reference that helps to support the structure of the shell and mitigates potential failures in the model.

The other options may not necessarily address the specific issue of maintaining a stable transition when removing faces adjacent to blends. For instance, simply removing all adjacent faces could lead to greater instability and more errors, while opting for larger wall thicknesses doesn’t directly address the issues related to blend interactions. Adding edge faces before the blend operation can also complicate the geometry rather than simplify it. Hence, incorporating a shelf face at the tangent edge stands out as the most effective approach to prevent failures in this scenario.