Hi Dodo764 and all users!
I have the "same problem"...Firmware on the Wii-U is 5.2.0 E and I would like to make a softmod, but I was afraid not to spoil the console :(
By the way I have all the necessary lego batman (org wii) and sd card 2GB. Now, what should I do... softmod, be or not to be...