Step 7

Import the "Lug" primitive, select the upper part and move it up to extend the foot part of it.

Step 8

Select the side-base CPs and move them away. From the Birds-eye view, break and delete the bottom splines to make an opening at the base and then detach the remaining bottom corner splines.

Step 9

Copy-paste the next lower spline contour, move it down and move the outer CPs away in both directions. Select the CPs at the end of the bottom corner splines and move them such that they align with the new base contour CPs. Glue them to the base contour.

Step 10

Select each splines that joins the base contour and make them smooth. Shift drag the bias handle so that it is completely horizontal. Change the Magnitude to 100 if needed.

Step 11

To remove any surface discontinuity, the bias handles must be in line with the incoming spline. Unfortunately, the "zero slope" attribute that is available when editing channels is not available when modeling.

A low-tech way to accomplish this is to paste a "Post-it" note on the screen such that the edge is along the incoming spline and then shift-drag the bias handle until it is in line with the "Post-it" edge.

The exact method would involves calculating the angle between 3 points which can be performed efficiently with an appropriately designed excel spreadsheet.

Result

Here is the Lug