I have not had a chance to test this out yet. I have requested an old chuck
from our Machine Tool Supplier so hopefully I can make the mods and prove it out
before commiting to my main chuck.

Are you sick of constantly making bungs/rings/spiders or whatever else you use
to clamp onto whilst machining your jaws in situ.
This method slides and clamps against the keys which are machined into a position
around 1mm away before the actual physical closed position.
Thereby forcing the jaws outward as if clamping against a ring ready for machining in situ.
Simply move the keys out after machining the jaws.

Hopefully the following pics will describe what I mean.
Let us know what you think. I have a few ideas to overcome any discrepencies.

Edit :
I cant get the swf file to play so please click on it and open it on your pc

but the forse of hidraulic is much gtather then you think(I have same chunk) and minimum of working hidraulic preshure is 13bar Traub safety protocoll .
ps. movment of my chuch is 20mm so make the keys space biger and consider to make keys in difrent dimenzion so then you can turn lot of difrent dimenzion you can see my pet here
http://www.youtube.com/watch?v=MprcK6ViRGc   same chuch is on 2:04 min in video.

and consider to make keys in difrent dimenzion so then you can turn lot of difrent dimenzion

The keys operate below the surface of the jaw serrations which means the jaws can be mounted in any position and bored
to any dia as per normal.