Hey there. Did you end up figuring out how to add the extra levels to the game?
Viewing post in Bounce (2001) Remake comments
Hey! Here is the thing, I only know about those levels from the Wikipedia article. There is a link to an archived page with a download for the levels. I downloaded them and tried many things to install them to the original game's .jar archive (like replacing existing levels with new levels) but I couldn't get it to work.
However, looking at the archived page again, it looks like those levels were for a different version of the game, not the one I am remaking.
If you or anyone else knows how to play those extra levels (if they even exist for this version) I'd be happy to add them to the remake.