512(with the 800mhz processor)'s firmware is NOT compatible with 511(with 533mhz processor). Read it
here.
To be honest I dont why they still choose Vizplex over Pearl for this hardware upgrade when they are promoting the new 622 with pearl screens. they also need to work on a better product name, i mean are they just gonna name the next version "Pocketbook 360 plus New Improved"?