unfortunately, we doesn't support setting permissions in SCP (permissions are set to 644 by default).
The SCP is quite legacy file transfer protocol and we added SCP support for situations where SFTP cannot be used.
Is it possible for you to use SFTP which is quite newer protocol?
Using SFTP you can set permissions like this:
// initialize SFTP client object
var client = new Sftp();
// prepare new file attributes
var attributes = new SftpAttributes();
attributes.Permissions = (SftpPermissions)Convert.ToInt32("755", 8);
// set attributes of a file