Hi Michael,
A quick post to show you what I meant by the cut not having the expected result on each view.


Here I draw my curve from the front and trim on my shape. The cut is as expected on the front but it doesn't match on the side.








Now I made the cut on the side, and the result doesn't match the front =)






I guess it is normal and I have to draw the cut in both view.
But If I move the curve to meet both view we can see that it can't match the shape I built.
So I'm clueless :)