1st header:
Start:	Size:	Desc:
0x00	0x4		0x00000100
0x04	0x4		File Size (inc. header)
0x08	0x4		0x00000030
0x0C	0x4 	End of the ROM (not the file)
0x10 	0x4 	Start of the footer region (presumably an index for the PCM audio samples). Matches end of file/file size if PCM data is missing (according to 3dbrew.org)
0x14	0x4 	Points to the second header (starts with 3C, looks to be mostly the same as New 3DS's SNES VC header starting from 0x30)
0x18	0x4 	File Size/End of file? (same as 0x04)
0x1C	0x4 	0x00000000
0x20	0x4 	Points to the file end (Secret of Manae kind of a flag?)
0x24	0x8		Wii U Virtual Console Game ID (WUP-J**X, X — title region (E for EUR)?)
0x2C	0x4		0x00000000

2nd header (0x3C...):
Start:	Size:	Desc:
0x00 	0x1 	Emulation speed in FPS (0x3C == 60)
0x01 	0x3 	ROM size
0x04 	0x1 	0x00
0x05 	0x3 	Size of the converted PCM audio samples region (starting after ROM). 0 if PCM data is missing (according to 3dbrew.org)
0x08 	0x1 	0x00
0x09	0x2 	Footer region size. 0 if PCM data is missing (according to 3dbrew.org)
0x0B 	0x2 	0x0000
0x0D	0x2 	Game preset ID? (varies for each game) (according to 3dbrew.org)
0x0F 	0x1 	Unknown (0x02/0x03, mostly 0x02)
0x10 	0x1 	Sound volume (according to 3dbrew.org)
0x11 	0x1 	ROM Type (LoROM/HiROM)
0x12 	0x8 	0x0000000000000000
0x1A 	0x4? 	Unknown (mostly 0x00000100)
0x1E 	0x4? 	Unknown (always 0x00000100)