But 8-bit sounds terrible. Especially when the sound gets quieter you hear lots of noise through it. Reducing the sampling rate to 22050 Hz is a better idea. You lose the highest frequencies in the sound, but not a lot of sounds have that much of a frequency range anyway so you won't notice. And it cuts the size of your sound in half.
I think Generals also accepts IMA ADPCM format WAV sounds though (like RA2 did), and those have a lot better compression than plain PCM WAV. You should see if you can convert to that, it saves even more size.