Solaris net boot from Linux

I've spent a couple of hours Googling for this with limited success.
Can anyone point me at any FAQs/HOWTOs/whatever that covers this? My
problem is:

1) I have 2 dead UltraSPARC/SunOS 5.x boxes, and I need to do a net
boot of some sort so that I can carry out surgery on them

2) I have a Centos/x86 box that I would like to use as the boot server
(note that this isn't a Jumpstart installation: I just want to boot,
so that I can then manually mount disks, edit the password file, and
so on; hopefully the SunOS machines will be able to boot themselves
afterwards)

3) I have another working SunOS machine, so I could presumably use the
kernel from this one, but it might be easier to use a generic Linux
SPARC kernel (if I can find one somewhere!)

4) I can't use the working SunOS machine as the boot server, since it
doesn't have the boot server installed, and I don't have the CDs

The 'network booting service' on out-of-the-box RHEL/Centos doesn't
seem to be appropriate; as far as I can make out, it only handles
Jumpstart installations if you've altready got a CD (which I haven't).

Thanks -

Paul
.