I see. The way I got around this issue with one of my games was to speed up the sound samples by 2 octaves, so they squeeze down to just one third of the original size. Then just play those back at 300% slower speed. Thats how they did it with the Domark Star Wars game, so just an idea.
I took another path (because sfx were taking really too much space), silenced some sfx & music, only left a few ones (shoot, jump, die, fall...) and it's not so bad, and it runs on OCS.