you take well defined bin similar to your ecu (same hp, bin file size etc)
open BC3, select hex compare, load that same bin at left side and your bin at right
open xdf in tuner pro and save it to yourname.xdf
select any parameter, press F2 and remember its offset. do not close this dialog
open BC3, press go to button and type this offset (left side must selected)
now look to the bottom of the right side - you will see your offset. just replace it in xdf (same way to axes) and you ve got your own defined parameter

beware this way not 100% accurate. so always compare resulting maps of your file and those file. if its not the same - check it twice.

S4 ME7.1 551G vs 551M are very similar.

G box is completely defined.

If you want to be helpful, actually, start making a k-box based on the m-box xdf