Sorry for replying so late, january was a really busy month for me
First of all IBS is following an own versioning of the firmware, so don't rely on it! So here i'm talking about the IBS2.1.3 and the PB2.1.2 firmwares. PB2.1.2 is NEWEST than IBS2.1.3. I dislike the ibs firmware customizations so i decided to install the PB2.1.2 firmware. Before installing PB2.1.2 i updated to IBS2.1.3 and it appears to be based on the PB2.0.6 firmware. It is slow on writing and misses some useful apps from PB and the IBS2.1.3 browser is definitely worst compared to the one on PB2.1.2.
After the IBS2.1.3 i've manually installed the PB2.1.2 W/OUT formatting internal memory and now i have the PB2.1.2 with the Zingarelli dictionary and native note taking feature
After every firmware update remove the firmware related files from internal memory and/or sd card or any future firmware update via wi-fi will fail (at least it failed for me)
Hoping this helps if not let me know how i can further help you!
P.S.:I'm an happy PB603 (Leggo IBS) owner, now!