I would still love to try with someone's update files to see if I can use the full 1TB, but I did make it work by limiting to 500GB, without having any files from my old hard drive. I followed the instructions in the first post, skipping the copying from the old drive, and making the small below change to the xboxonehdd script (based on the size of my old drive, may be smaller than needed though). I then put the OSUDT2 "$SystemUpdate" folder on an NTFS formatted flash drive (according to
http://support.xbox.com/en-US/xbox-one/console/offline-system-update-diagnostic-tool), and booted using the flash combo (side button, eject, and power until it "power on beeps" 3 times total). It updated, then went through the setup process.
--- xboxonehdd-master/xboxonehdd.py 2013-12-01 15:41:45.000000000 -0500
+++ xboxonehdd-master-limited/xboxonehdd.py 2016-02-23 15:31:20.986030359 -0500
@@ -87,11 +87,13 @@
# calculate user partition size to nearest GiB
total_size = int(open(path.join('/sys', 'class', 'block', sys.argv[1], 'size'), 'r').readline()) * 512
+ # Making it fit in original 500GB size...
+ total_size = min(total_size, 500107000000)
user_content_size = (total_size - sum(PARTITION_SIZES))/1024/1024/1024
PARTITION_SIZES[1] = user_content_size*1024*1024*1024