Hi Steve, if these areas are to be flush:



Then I'd probably try something like build an initial surface that extends over to start with, and trim it with your profile:



Then discard this piece:



Then also discard this piece:



Extrude out your profile a larger distance so it goes past the new surface:



Trim it with these as the cutting objects:



Select this as the piece to remove in the Trim:



So then you'll have just one larger surface for the inside like this:



One problem with your original model is that this spot did not go all the way across:





- Michael