Step by step guide:

Install 11iV1
Mount V2 media (via nfs or whatever)
swinstall -r -s /hpux11iv2dist /Update-UX \@ /var/adm/sw/update-
ux.root
vi update-ux , find chkValidHardware() function
change return ${FAILURE} to return ${SUCCESS}
update-ux -s /hpux11iv2dist -x match_target=true
vi /etc/rc.config.d/xfs to re-enable xfs (otherwise CDE won't start)
reboot!

# uname -a
HP-UX vision B.11.23 U 9000/785 2002802175 unlimited-user license
# /bin/model
9000/785/B2000

that's all! no problems so far, runs smoothly!