attachment_fu file perms

I have attachment_fu running for some photos and have 2 nagging problems
I can't seem to resolve.

1. I want to change the default file-mask attachment_fu uses on all the
files it generates (original and thumbs) and didn't know if there was a
way to do it without actually invoking file ops from the ruby code (e.g.
a flag I can set somewhere)

2. When I set the processor to none and change the file-types allowed,
then upload a file, it goes through then complains that it couldn't find
image_science (which of course I dont want it too because I set the
processor to none)