Sweep along 3D Sketch with Guide Curve

Hello,

Let me begin by stating the end goal, since I may be going about it entirely the wrong way.  I'm trying to add a 3" wide flange around the perimeter of part.  See the pdf sketch.  I've gotten a small portion of the flange added surface extruding the trailing edge face; it's in yellow on the model.  I think the correct way is to sweep along a 3D sketch with a guide curve.  I've tried sweeping the flange sketch along the 3D sketch w/o a Guide Curve and the result isn't right.  I would like the flange to remain mostly tangent to the wing tip (see pdf sketch), though exactly tangent isn't required.  I guestimated a projected curve that is my tentative Guide Curve, but get a wavy and bad result when I sweep with it.  If I'm on the right track, can someone point me in the right direction, or suggest a new route if I'm entirely wrong?

Thanks,

Stephan

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