You can find this at http://wlug.org.nz/UDev which has links to a number of websites.
Thanks, I seem to have it figured out now and added my experience to the wiki. Hopefully I can get Verne's system sorted out tomorrow.
One little tip - what I would do is name the devices (using udev) something like /dev/soundev1, /dev/soundev2 or similar rather than variations on dsp as it seems like you can't lock down a pre-existing name. You can, you just have to be sure you handle all possible devices uniquely so the kernel never gets a chance to put something else there first. Renaming the devices is probably safer but Verne's scrips all refer to /dev/dspX and he doesn't want to have to change them!
For example my ethernet cards are lan0, lan1 which are locked down and eth0/1 randomly change.
That's what most of the documentation suggests.. but I think swapping them would have worked in your case too.