Thanks so much for the advice. I decided to go ahead and reshape for chunk size for the experience, so when i've got a raid-full of important data i know what to do about adding a drive. My computer locked up on me around 6% but i was able to recover using:
/[pathto]/mdadm -S /md0 /[pathto]/mdadm --assemble /md0 /dev/sdb /dev/sdc /dev/sdd --backup-file [path_to_backup_file]
Ubuntu tried to reassemble on boot, but failed. After manually assembling and mounting everything works as normal.
Another thing that hung me up... your guide said to use --chunk-size but the parameter is actually --chunk.
Other than those few hiccups it's going smoothly. I'm thoroughly impressed that i can still use md0 as it rebuilds. I'm able to play music and video from the raid while encoding a video to the raid with no perceptible slowdown. The only way i know it's slowing down is from the readout from /proc/mdstat.
Last thing (for now)... is there any reason to keep the packaged version from ubuntu if i've got the latest from source?
Thanks again! justinmteal