PRS-T2 Firmware updater: bypass version checks?

Hello!
I recently purchased a PRS-T2 (European version) with firmware 1.0.04.11081... and, obviously, immediately tried to root it. However, it seems locked.

I seem to have found a way to bypass version and model checks in PRS-T2_UPDATER_*.EXE but... now I am stuck again:
- Re-installing 1.0.04.11081 (whether EN or US) works, but doesn't allow jailbreaking.
- Actual downgrading seems to work at first, but displays an error message after automatically rebooting the device.

I guess a second set of version or checksum verifications is happening on-device; any thoughts?


Here is the method I used:

1. Do not run the executable; instead, unpack it with 7zip.

2. Edit "PRS-T2_UPDATER_*\eBookUpdater\scripts\updater.xml" :
Remove "// check model name and is specified revision as well" and the following 4 lines.
Remove "if (this.isNewerOrEqualVersion(version)) {" and the following 5 lines.
Don't touch the next few lines (Starting with "this.") but remove the two lines containing only "}".

3. Launch upgrade using "PRS-T2_UPDATER\Reader Updater.exe"!