Nokia Lumia 1520 - How to Update To 10166 (Slow Ring)?

Not sure if this is the correct area to post this but I have a Lumia 1520 that I have previously had the insider preview on (Fast ring). However I need the portable hotspot work (as you know this is broken in the latest build 10512) so I would like to install build 10166 (Slow ring). So I reset my phone to 8.1 using the recovery tool, installed the Windows insider app and selected slow ring. However the phone just updates to Windows 8.1 update two even though it should go to 10166. I've checked the app the phone is still set to slow ring. Ive also reset the phone and tried again... same issue.

Any ideas?
Nathan