A few questions...

[Sandman]

In Gecko OS I can load my custom menus just fine.  However in Riivolution, it does not load them at all.  Is this normal?

In Gecko OS, my custom soundtrack's custom titles show up just fine.  However in Riivolution they do not show up at all.

In Gecko OS, is there a file size limit?  Because I put up a bunch of songs on my SD card (around 18 songs) and the game freezes after the loading screen.  However Riivolution loads just fine (I know this has an unlimited file size).  I even deleted almost all my textures, and it still didn't work.  

P.S. I use Brawl with Codes in Riivolution, because I honestly don't know the difference between Brawl +/- etc.

[Segtendo]

Menu issue-The file is named mu_menumain.pac, right? Riivolution reads the files as if they were on the disc, so you need to add an _en to the end of mu_menumain.
Music title issue-The file's name is info.pac. It, too, also has an _en at the end of it to be read in Riivolution.
Gecko-I believe Gecko has file size limits, but I'm not sure about Riivolution.

[(specter)]

Well I can't answer your Riivolution questions as I don't have it, but I'm pretty sure Gecko has limits, but your issue with the songs freezing after the stage with only 18 songs is probably due to something else. I have about 56+ songs on mine and I never get freezes.