[Grml] udev rule for usb boot device

[Mark]

What is the best/approved udev rule for a usb hard drive to escape
random drive letter variations /dev/sd[a|b|c|d].  The drives have
ATTRS{serial} but I want to walk carefully amidst grml's built-in rules.
 For example, if sandwiched between other grml rules, what lexical
filename to use.

Second question: will the udev name work from /etc/fstab during boot, or
should we stick to mount-by-label.

(Idea for grml2hd - use hostname to auto-generate a related udev naming
rule for the drive.)