keeping portageg files in another directory tree, and creating a symlink ln -s otherdir /usr/portage works with non-cvs packages, but upon attempting to emerge a ...-cvs packages access violations are reported "can't create dir", regardless of using or not using "FEATURES=sandbox userprivs usersandbox cvs" a quick work-around would be to mount --bind otherdir /usr/portage, rather than to create a d of symlink.
please test with new cvs.eclass committed today.
fix has been tested, works fine.