I was fighting with a application enviorment migration from WPS 5.0/ to WPS5.1/RAD6.0. I found some interesting facts that I thought worth scribbling it here. First of all RAD 18.104.22.168 doesnt have support for Portal/Portlet development. The good news is that IBM has released an update for this in its newst RAD 22.214.171.124, so just update the RAD enviroment always to the newst and greatest!
If you have a Portlet application there are few tricks you must adopt to migrate the same to the newer enviorment. First create a blank Portlet application using RAD 6.0. Then manually copy all your source files from the old project to new project. Then make sure all dependencies are configured as of the old project. While copying portlet.xml and web.xml make sure you overwrite the new files with your old files. DO NOT overwrite portlet.tld, you must use the new portlet.tld. Also while copying lib directories DONOT overwrite with old JAR files.
If you follow these steps then migration to newer enviorment must be a peace of cake. I recommend atleast 1.5 GB RAM for running RAD 6.0 and WPS 5.1 (or even WAS 6.0)!