Keith- I've been thinking about this all damn morning. *:-) *I've come up with a few things (It's kinda tough to describe this with simple words, but I'll try)....
I don't think it's necessary for fingers to bend "backwards" as much as they need to bend "flat" at the first knuckle. *This will help you cover two strings with only one finger. *The tough one to get "flat" (and precise) is the pinky. *Think of it as a micro-barre. :-)
In the caboose of that train of thought, it helps to be able to "angle" all your fingers- where you only use the very tip of your fingers on a particular note, keeping them 100% clear of all the other strings. *This is VERY helpful, and something good to practice, esp. the pinky.
I was learning some Malmsteen stuff a LONG time ago...
(how long? *Let's see...I was learning it when the Dead Sea was just Sick! LOL)...and I picked up a little trick:
Instead of doing the micro-barre thing with my index finger, I moved my ring finger to the appropriate note. *In the example below, the ring finger is done doing it's job, and the index finger is on it's note, so I quickly move the ring finger to the "other" note that the index should/could cover. *
Maybe it's time for a visual...
------------------12-17-12--------------------
---------------13------------13----------------
------------14------------------14-------------
---------14------------------------14----------
-----15-------------------------------15-------
--17-------------------------------------17----
Now, here's my fingering
(1=index, 2=middle, 3=ring, 4=pinky)
------------------1-4-1-----------------
---------------2----------2--------------
------------3----------------3-----------
---------1----------------------1--------
-----3-----------------------------2-----
--4----------------------------------3---
I've shot a video clip of this sweep. *It was shot REALLY early in the morning, and with no warm-up, so you'll have to excuse the un-cleanness of it and the lack of
Rusty Cooley-esque speed. *:-)
IM me if you'd like to see
(me hack through) it. *(It won't load into my email. *Sorry.)