The concept: Seperate common Actionscript 2 classes into seperate .swf’s and load them in when they are needed creating shared classes. The tool that automates this process and reduces your filesize in the process: Ariaware’s Optimizer. Ive been running some tests with it on some of of the applications ive created in the past that utilise more than one Flash Movie and use the Version 2 Components and have seen dramatic filesizse reduction (36%). You can download a 30 day trial version here and give it a go for yourself. Youll be impressed!