This method works just fine, here is how you do it. Download a fresh RA or just copy and paste your current one, then go to manage emulators in Launchbox and add a new emulator call what you like then point to the second Retroarch .exe. Then go to your assoiciated platforms tab and make sure it has the correct core for the system, then click your master system in the left bar click a master system game then ctrl a to highlight them all, then right click and choose edit. In the first dropdown choose emulator, then the second box choose your second Retroarch. You will of course have to set your options and overlay and save the core override like like i described in your other thread.