Re: Adding EE packages to LXDE spin
The package spin-kickstarts provides the package fedora-kickstarts that contains the kickstart files for building livecds. In these kickstarts files you will find the list of packages that are included with the spins.
So like stevea suggested, take the package list from fedora-livedvd-electronic-lab.ks ( I believe that is the one you are looking for) and use that list as a reference to install the packages you are missing.
Hope this helps,