You can find a 8.398 for X50 devices here : Post#55
Password : downunder
Basically the same as the 8.396 you currently use.
It will reboot once after the first the start and you have to shut down the device either using the menu function for that or by holding the power button for 15+sec.
The recalculating problem that can occur after you set everything up and restarted the device can sometimes be solved by activating the shutdown on power loss in the battery saving settings.
For the XL I could try to modify the 8.398 a bit to give you more free Ram if you want to try it.