you do realize flashing emunand to sysnand will just give you a stock FW of whatever FW emunand was using, and yeah flashing to 8.1 or higher seems to cause bricks......so this process is not advised and somewhat pointless
if you really want to do it for whatever reason, you will need to extract your emunand using emunandtool so its formatted correctly, if anything messes up the only way to recover is with a hardmod
but just to clarify any of the features of 7.x emunand are lost, i.e no region free/FW spoofing etc, it will just be a stock 7.x