Hi Bravlin, some of the naked edges could be coming from some new bottom surfaces that no longer align with the original extrusion.

The process for reverse engineering the extrusion is kind of tricky, the steps are something like extract the edges as curves, prepare some cutting lines to cut away portions that are not on the silhouette, trim the curves leaving no doubled areas in the Y direction, then compress it in the Front view using the edit frame corner grip with "Flat" snap.

That will then leave the flattened silhouette which can be extruded. It's also good to rebuild it to reduce segmentation and also there are a few spots where control points get very nearly stacked up at the end of some curves and those need a little adjustment to move the first interior control point.

When that is extruded it is then accurate enough to be trimmed with those edges, except at the bottom where some new surfaces stick out a little more than they did on the original. 3DM model file is attached.

Here are some screenshots of the process. At some point I want to make a curve silhouette tool to automate these steps.
















- Michael