I've tried this script: https://googledrive.com/host/0B0YvUuHHn3MndlNDbXhPRlB2eFE/cros-haswell-modules.sh
(via:http://realityequation.net/installing-elementary-os-on-an-hp-chromebook-14 , section 5) which seems to work for owners of other chromebook models, but not for me.
Beyond that I'm not sure what to try. Any suggestions would be appreciated.