I'm not Roger, but as far as I see it these are the options I could come up with:
1) Buy the Apex break out box and a float switch that mounts higher than the Tunze 'too high' float that cuts power to the Osmolator in the event that float is actuated.
2) Set the outlet for the osmolator to only run for a very small window of time per day, the chances of an overfill here are slim. Though this isn't entirely ideal if you are trying to keep your salinity as stable as possible throughout the day via small top offs. You could have a couple small windows throughout the day to help alleviate that issue, or perhaps even an oscillation function for the outlet to allow the outlet to turn on for 5 minutes every 4 hours or something.