Hello, find attached, I have baked out the rail and profile- this is going to be a fabricated rail so it needs to always be a consistent width etc- that is why the profile at the end are at 90 degrees to the vector of the arc at end and start points.
iam not sure what you try to achive but you probably get the same result with sweep 1 when you use the arc as rail and add another, smaller section in the middle of the arc.
or you could creat another section in the middle and loft the sections.