They may tend to slip a little bit from their normal places, causing you're guitar to go out of tune.
I had the same problem, and to get over it I used to make the pickups face the floor when I pull so far.
But I later found 2 solutions for this:
1- Lock the thing that hold the springs more into the wood by the 2 screws at the back of the guitar... you'll have to either remove a spring or increase the strings gauge.
2- Wrap some kinda rope around these springs and the bridge... I'm sure you can manage to do that.
Also I saw a picture (I think on http://www.jemsite.com) , and the springs were locked to the block that hold them to the bridge by a small bar or something, does anybody knows what is this thing called?!...
As you can see, I'm very bad with technical terminology ... hope somebody can translate my post into english. :)
[Edited by SLY on 12-26-2002 at 10:15 AM]