So, about the music.
I said it few times, but no one seem to noticed it :/ (probably posted in wrong places though)
Right now, every music in the OST plays twice per file. It's a waste of space. Instead of reducing it's quality, cutting the music in half and taking care of proper loops would be much better. It would sound the same, but take less space.
Looping this might be a problem though, because the music doesn't loop perfectly and it's slightly less noticeable if it's longer. It should be possible to make a script that takes care of this, but I don't know how good would that work in RPG Maker.
Anyways, doing this, I was able to reduce the size of Atmosphere - Light Realm (I just used it somewhere >.>) from 10MB to 3MB, without noticeable loss of quality.