Texas two-step: help needed on 2-drive upgrade steps

Situation: 2010 iMac with 2TB drive + optical. Slow. Drive filled.

Actions:

- Bought 240GB SSD from OWC + "data doubler" = goodbye optical, hello SSD. Blazing startup on Yosemite now.

- Bought 5TB HD from OWD and installed. 2TB original now sits in a USB enclosure

Problem:

- I want to "restore" my 2TB, with bulk of files now "re-homed" on 5TB

- Migration Assistant tries to move everything to SSD -- even when I de-select almost everything. The "other files" are massive and make it impossible to just move over the accounts.

- I have tried using CCC to copy /users/ from old 2TB to new 5TB, but permissions aren't working when I point new accounts to /volumes/5tb/users/foo

- I didn't turn off FileVault2 when the 2TB was installed, which could be the prob there. I could "fix" that by booting from the 2TB enclosure, but will take days given slow USB 2.0 connection on this iMac

- To reiterate, I can create new users and re-point their "home" to the 5TB. But the permissions are different and files / mail won't open.

Request:

- How do I properly restore this external drive to this new two-drive system?