Specifying coding system for Imap.cache files

When running vm on a Windows machine, I typically add
( "^C:/myhome/mail/" 'raw-text-unix) to the alist file-coding-system-alist since I want to keep all my
mail files in the unix file system coding without the annoying carriage returns (^M) at the end of each line.

However, this doesn't seem to be working for the imap-cache folders even though they are stored in the same
mail heirarchy...

Unfortunately, these ^M characters then seem to sometimes generate an error when reading imap mail since
the coding system gets messed up.

So, is there any way to get the imap-cache files to respect the file
coding system that I am setting for their directory? i.e., is there a way to specify the coding system that vm
uses to write to an imap-cache file?

Thanks