Have you tried covering the crate with a sheet so the cat can't see out? It is amazing how much more secure a cat will feel if the cage/crate is covered. It is almost like they think if they can't see you then you can't see them. We used the sheet covered cage with all of my Mom's ferals on the trip for spay/neuter. Worked wonders - non of them made a sound once the cage was covered. Should be a dark color sheet to minimize the amount of light that gets through. One caution, make sure it isn't too hot under the sheet.