I have a flat, planar edge, that forms the base of a part. The angle of the two faces that meet at the edge varies along the edge. When I fillet that edge, I end up with a surface that is not flat anymore (so the part would not be quite upright when resting on its base). Is there a way to round the edge that keeps it flat?

I attached a sample 2015 SLDPRT file. The edge I'd like to fillet is parallel to plane4. I'd like to fillet such that the filleted edge is still parallel to that plane.

To illustrate the problem, I added a sketch with lines to plane4 and I measure the minimum distance between the lines and edge. Before the edge is filleted, the distance to lines in plane4 is constant (4.81mm), as shown below:

But when I fillet the edge, it no longer is flat with respect to plane4 (dy varies from 6.07 to 5.35, below):

Thanks for any suggestions!

once more in SW2014