Rhino 3D: how to convert curve to cookie cutter

Hello,

Using Rhino 3D, does anyone know how to take a closed curve and convert it to a solid extrusion which has a consistent wall thickness around the entire perimeter? This is easy for things squares or circles that have symmetry around the axis of extrusion, but not with shapes like hearts or rectangles because they don't scale equally in all directions. With a heart shape for example, you can't just clone it, 2D scale it slightly smaller and Boolean subtract it from the core of the original and have the same wall thickness around the perimeter of the resulting object because the heart curve will not scale equally in all directions from its center point. I'm using the area centroid finder to pick the center point of the scale operation but it just doesn't produce a second inner curve where the distance to the outer curve is exactly the same around the entire perimeter.

Any help will be apprecited.

I didn't find the right solution from the Internet.

References:
http://forum.makergear.com/viewtopic.php?t=2218
Datacenter Management Video

Thank you.