The enclosed model is typical of customer supplied part models for thermoforming. The task at hand is how to efficiently extend the lower (red) edge of the shelled part by about .5in. to prepare for making a pattern. This is only one step in the process which results in a "mold" of the inside of the part.

This particular part has 1 deg. draft on the "outside" walls.

A simple extrude does not work in this instance because the needed extension has many directions, not just one.

In the past I have constructed a sketch on an offset plane and lofted between this and the original part edge. This is often tedious but works well.

The extension faces must blend with the original part faces.

I welcome your input, and thanks in advance.