All you need to do to get Mixer to work is, after you've installed the mixer software, edit the startup sequence so MUI is started before mixer is started as the software requier MUI and crashes if it's not running (would be nice if it stated MUI missing but no... CRASH!).
I've only worked with Voodoo3 myself so I can't help you othre than to say that the P96 needs to be installed selecting CV3D as the videocard though it's not the correct one and after that manually edit the monitor file to fit the actual card you have installed. After that edit the screenmodes using P96Mode and make sure no screenmodes use "interlace" as atleast Voodoo doesn't handle this (resulting in the screen get filed but with only half the actual graphic).
