recovering data from a truncated vn-file possible?

[Josh Brooks]

Long story short, I have a 4gig vn-backed filesystem.  The file backing it
is now missing the last 750megs ... I can vnconfig it, but when I fsck it
I see:

# fsck -y /dev/vn1
** /dev/vn1

CANNOT READ: BLK 44109856
CONTINUE? yes

THE FOLLOWING DISK SECTORS COULD NOT BE READ: 44109856, 44109857,
44109858, 44109859,
ioctl (GCINFO): Inappropriate ioctl for device
fsck: /dev/vn1: can't read disk label


Is there anything at all I can do to get data out of this ?  I know some
of it (750 megs worth) is gone for good - but can I get any of the rest of
it ?  Presumably, when mounted, this was only 50% full ...

thaks.