The speed report tool is greatly exaggerating the potential compression savings that are available. Most of the floatbox files are already minified, except the copyright notices and the editable preferences.

It's not true that you need to change floatbox plus source code to run minified floatbox files. Floatbox ships with only minified files. There is no possibility of running anything else.

If you want the best compression, enable your server to serve the gzip versions of the files, included in the floatbox download. There's some info on how to do this in the floatbox instructions.

Cheers...
...Byron (floatbox author)