Hiya.  Sorry about the delay responding, I was
out of town.

tx_ticks and tx_retries is definitely what you
want to use at the command line, to change the
timeout to detect a dead node, when traffic is
being transmitted.

The defaults work out to 10 seconds, which may
be too conservative for you.  Try dropping tx_retries from 25 to 5 and see if that helps.

As a test, talk to a node that you know is up, 
via something like "ls /net/fubar" then unplug
your network cable, and run "ls /net/fubar" again.

You should see a delay, then something like
this:
 
  ls: Host is down (/net/fubar/)

At that point, you can do a:

  # cat /proc/qnetstats

which will tell you exactly what happened,
and when.  Hope this helps!