artadmin fills /tmp during dump

It would appear that artadmin is not very well behaved in its use of the /tmp folder during a dump of a full repository.  I have a repo that has reached 40GB (under 1.2.5rc5) and am trying to export. I started to get messages like ...

Failed to export jcr file: 'path/to/file'. Skipping file

I have worked out that this is because the /tmp folder (2.5GB partition of its own) is filling up and artadmin can't write it's temporary files to it.

So I tried setting the environment variable 'TMPDIR' to point somewhere where there is plenty of space, but artadmin appears not to honour it as it kept right on writing its temp files in the /tmp folder!

I have managed to keep the export running by manually removing files of the form bin[\d]*.tmp from /tmp during the dump process.  This is not very satisfactory though.

My question - has anyone seen this behaviour already ( a search of this forum did not seem to find any discussion of it)?  Is there a better way of keeping a large repo dump going with a much smaller /tmp folder?

Thanks
Damon