You might be able to find something at /usr/share/doc/fspanel*, or, maybe, fspanel will create some rc file in your home dir when run from first time. Hopefully, that file will also have some hints on how to configure fspanel. You can search for ~/.fspanel* or ~/.config/fspanel* or something like that. The old fspanel web site seems to be down, I have no idea if there's any other place to look for info right now.
You can also check fspanel --help and see if there's anything relevant in there.