It appears that the Sony EX cameras exhibit the same form of IR sensitivity that the Sony F35 and the Panavision Genesis do. Therefore the best filter for these cameras is not an IR Hot Mirror but instead a Tiffen IR ND non-Hot Mirror filter. This filter set was created for the F35 and Genesis. It is also less expensive than the Hot Mirror type filters such as the Formatts we sell for the RED.
Please note that different types of cameras and sensors require different type of filtration. The Formatts remain the recommended solution for the RED but the Tiffen non-Hot Mirror product is best for the EX1/EX3.
Art Adams over at ProvideoCoalition.com is doing an IR Filter Shoot Out to see how filters from three manufacturers work with the RED, F35 and EX Cameras. You can check those tests out here.