Some of you may have seen my last question about merging the two faces on my plenum design... needless to say I've hit another road block.

I'm attempting a swept cut. I need the bottom of this object to be a perfect oval, with the two semi circles at each end tangent to the straight edges of the oval. For this to happen, I believe I need the swept cut to cut the swept profile perpendicular to the path, but for some reason that's not happening (as you can see, the arc lengths are not equal). Photos and part file attached. As you can see, the profile is not perpendicular to the path towards the base of the object. I did not encounter this issue with the other swept cut I made on this part. Any suggestions?