Please provide a solution to the fellow reefer's noise problem then. All you stated was that the Shadow was improperly designed. This is just a uneducated guess as you have never even used one of our shadow overflows. You mentioned this "The problem is that the external box is improperly designed. The external box should be as high as the internal box which will fix multiple issues, 1. prevent potential overflow during startups and 2. allow to set your water height inside the box properly. " This is not a solution, just a bash.
I will address what you said and explain why this is incorrect. Again improperly plumbing anything can cause issues.
1: With the Shadow the rear box lid is sealed and creates a vacuum thus NO water can escape during startup. Also the 1.5" plumbing also makes it impossible to overflow during startup. Again this is dependent on the plumbing that the user does. Sure you can put 3 pipes in there that are higher that the top and flood anything.
2: This makes not sense as it is very easy to set you water height inside the rear box when it is plumbed properly.
Stop by our booth at MACNA this year and we will personally show you this overflow in action.
Please refer to our main thread
https://www.reef2reef.com/threads/the-shadow™-overflow-from-synergy-reef-has-arrived.264816/page-16#post-3847620 for more information as we answer most questions there pretty fast.
Incorrect as we have lots of people on here that run well over 4000 GPH and have made it silent. The recommended pipe sizes are meant to be a basic starting point. They are not the only size that works. All tanks will require some tweaking of the pipes. The pipes inside the rear box have to be adjusted to your flow rate in order for the overflow to be silent. Changing the amount of flow means that the pipes need to be adjusted as well.