Since it's in the host's best interest to squeeze as much work out of you as possible, negotiation is sometimes necessary. CIES can help here as well. Include the host's reply to this letter in your application. The lack of this documentation will set you apart. The Project Statement is critical.
Results are more important than background.
Select your references according to how well they know you rather than how famous they are. Adjust all elements to support the project statement, including your CV . Include syllabi if you're applying to lecture. Ask your references to address your classroom skills.