I can’t be the only one with a poorly designed black tank.

One other thing that could be helpful...

Maybe if every time before you do a #2 in the toilet you first do a quick 3 second flush to send water down into your black tank and therefore onto the shelf. Then, maybe when you flush your business shortly afterwards it will drop down into the main part of your waste tank because maybe that shelf will already be wet and a little slipperier. Just a thought.

-Chris