Trailing slash mode = AutoRedirect means "The client is redirected to the matching URI. That is, the client receives an HTTP response message with Status 307 that redirects to the matching URI."
If a service doesn't want clients to present URIs with trailing slashes, then I would have thought that 301 (Moved Permanently) is more appropriate than 307 (Temporary Redirect).
Re. 301 from RFC2616: "The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs."
301 makes more sense to me. Or do you have special reasons for choosing 307?