Anyway first I let goo manager update me to 156, not realizing that was android 4.2. Everything looked and worked great except that I had to be root to write to the actual sdcard. Then, in order to start from a fresh slate so to speak I did a TWRP install then factory reset then EOS 4.2 nightly 156 again then the gbapps xoom only. Same problem. I did a TWRP external storage wipe. Same problem. Basically when running as the default android user I'm unable to write (possibly read too, not sure) to the real sd card (/storage/sdcard1). When I su to root, it all works fine, but that's not a solution for accessing the sd card from apps.