I don't think you can easily do this The sound files are tbs format and would need to produced with a sound editor, then tied back into the rc8 sound folder. Actually all the sounds in RC8 seem pretty good to me so this is not necessary for me anyway.
For real the sounds they come with the rc98 are very good but not radial sounds like the Saito fg90 or the best sound like an Moki 5 cylinder are missing. that would be awesome when they come one day.
