Changing the libSAVI tmp dir ?

This isn't a Sophie problem really, at least I don't think so.  I know
how to change Sophie's temp directory in sophie.cfg.

However libsavi.so seems to always use /tmp for unpacking archives.
I want to change this to e.g. /var/tmp, this is because /tmp is a tmpfs
in RAM, and putting up to 300Mb of archive in there (our users download
big files!) makes it swap quite heavily and hits performance badly.

Using 'strings' on libsavi.so suggests that it looks for TEMP in the
environment (that string is in the library), however doing "export
TEMP=/var/tmp" before calling sophie doesn't change things.  Has anyone
solved this already ?  If not I'll go ask Sophos, but I was hoping
someone might know.

Thanks,

Nick