I finally managed to exportfs the drive, I'm not sure if due to a combination of things in /lib/namespace or the -t flag in listen1 did the trick, or the combination of the two. I was happy for around 30 seconds, which is the time 9pfuse (9import) took to issue a "broken pipe" on my terminal, killing the connection to my remote disk. Pretty fed up of setting up a remote drive by now.