Not versed much in Flexi design but in Corel I use a "ClearClipboard" macro that is set to automatically clear the clipboard every time a file is closed.Or I can hit the CC macro myself when I feel it has large amount of data. This significantly speeds up the opening process of other files.
Also a good idea to regularly clear temp files. I have a batch file that does this in a flash too.My system runs fast and smooth.