Deleting ringtones from Sanyo mm-8300?

I am using bitpim to manage my Sanyo mm-8300. I had no problem adding
a ringtones to the "pc sync" area of my phone - until I reached four.
Now I can't add or delete or replace any of them. Is there a way to
delete ringtones from the pc sync area? Bitpim for this phone doesn't
support "replace" for ringtones, only "add."