Upgraded my CC unit from 1.5x and can confirm you need to do the full flash, thought it couldn't hurt to try from the update OS option but that did not work, told me the Nand was out of space...
Full flash worked as expected.
Doing the upgrade OS option really brought it home to me the amount of work that has been done on the OS side, as always many, many thanks for your (and everyone else's) efforts in supporting the Pandora. Well and truly above and beyond the call of duty IMHO....