Hi Marv, did Brian's suggestion above work ok for you or are you still stuck?

If I understand your question correctly, you're asking about making this piece shown selected here to mate up better with the circled area, is that right?



So I guess if a straight piece doesn't fit right you'll need to decide how you want a different type of shape formed that will fit, you could put in 2 rectangles and then use Construct > Loft to build a slanted surface between them something like this (shown a bit exaggerated here):



Or the way Brian is talking about is using Blend to make a kind of slightly "S" shaped transition shape, you can do that by drawing in some lines and then using Construct > Blend between the lines to generate blend curves like this:


Then you can loft between pairs of the blend curves to build surfaces.

- Michael