epix-0.8.8a.ebuild, when compiled in a sandbox, sets the INSTALL_DIR variable in the /usr/bin/epix script to: INSTALL_DIR=${PORTAGE_TMPDIR}/portage/epix-0.8.8a/image//usr (PORTAGE_TMPDIR is of course expanded....) This is because prefix is set to that in the makefile. The Makefile will need some more editing to Do The Right Thing; look at the install: section.
Added some sedding in the "prepix" file to change the INSTALL_DIR to be /usr. Please test.
Fix works. Thank you.
I guess this should have been closed long ago.