Horizontal Straighten - Example 2
Let's start with a panoramic image:

Select number 1 in the curve Segments list.
Add the first horizontal curve and set it like in the image below:

Select number 5 in the curve Segments list. The image should look:

Select number 1 in the curve Segments list. Add a new horizontal curve like in the image below:

Set the curve to the curvature like in this picture:

The curve is recalculated to 2 curve Segments for precise setting. Press the button "Straighten". The result should be like this:

There is no need for Ratio Adjustment.