I’ve been looking at the CTC forum. Yesterday CJ (Chris Juden) posted two items which I think will interest you:
http://forum.ctc.org.uk/viewtopic.php?f=45&t=92645&start=165#p852275
http://forum.ctc.org.uk/viewtopic.php?f=45&t=92645&start=165#p852284
If you are not inclined to track all the way back through this thread, you might like to know that CJ’s first post quotes an earlier post by Si:
http://forum.ctc.org.uk/viewtopic.php?f=45&t=92645&start=150#p851717
which in turn quotes a post by JohnW:
http://forum.ctc.org.uk/viewtopic.php?f=45&t=92645&start=135#p851589
Plenty to think about here.