I have discovered that Dolphin is able to read >2GB now, however "Read Failure" errors will begin occurring if ~1.95GB of data is added to sd.raw (regardless of sd.raw's size). I raised an issue for this problem (https://bugs.dolphin-emu.org/issues/8823).
After looking at mksdcard documentation (http://developer.android.com/tools/help/mksdcard.html
), I realized a virtual SD card of any size can be created. I modified ifrit05's "Dolphin SDCard Maker v1.0.bat" to include a 4GB option for more room. The SDHC expansion code is not required for the resultant virtual SD image to work with Dolphin. My modification can be downloaded here (for Windows, extract before using): http://www.mediafire.com/download/713qu5m08tf8av9/mksdcard+menu.rar
1. Run "Dolphin SDCard Maker v1.0.bat"
2. Press the appropriate number to generate a virtual SD (SD.raw) of the specified size.
3. Once mksdcard finishes, a SD.raw file will be generated. Place it in the "Wii" folder in your Dolphin Emulator setup.
To change a SD.raw filesize option to something other than the given choices:
1. Right-click "Dolphin SDCard Maker v1.0.bat"
2. Select "Edit"
3. Find "start mksdcard.exe -l SDCard XM sd.raw" where "X" could be any filesize in megabytes.
4. Replace X with the size that you want
5. Run "Dolphin SDCard Maker v1.0.bat" and select the option you edited
1. Using a 4GB SD.raw caused a brief "Receiving Vault Data" message to pop up before Brawl's intro video started. Interestingly, this message does not pop up if my SD.raw size is 2 or 3GB.
2. Use a program such as WinImage to add files to SD.raw
3. Tested on Win 8.1 Dolphin 4.0-7015
If anyone knows how to solve the "Receiving Vault Data" issue, let me know!