I resolved this issue. For anyone reading this thread in the future: you do *not* need to fill in the port or pin numbers in the MPG 'Ports & Pins' when using a Galil controller, you can just leave them blank. You also don't need a brain file to make MPG work with a Galil. It just works if everything is configured properly. My trouble came with the Galil software choosing the wrong part number when it registers the controller. With the DMC-4143, you have to manually register it using the non Plug-n-Play option and choose the proper part number when you register it. This is complicated by a non-intuitive hidden function of needing to pressing the CONROLL key on your keyboard when you click on the assign IP address box, otherwise you can't manually enter an IP address (see the end of Galil Application note #4422 where they document all this). Anyway, MPG works well with the Galil .. just make sure you have it enabled in the Mach3 MPG section & Galil Plugin + have the current Jog Mode (press the TAB key) set to MPG.