Ballast bags keep emptying through empty pumps

Ok here is my problem. I have a 2003 SAN that originally had hard tanks and I piggy backed a 400 fat sac on top that was filled via the vent of the hard tank. I always had a problem with once they are 3/4 full the water is pushed back out through the empty pump (rule 1100 aerator). The easy fix is to push a cork into the outside of this hole and remove it when we are ready to drain. But, this completely does away with leveling the boat while riding. I've heard that running the empty hose up higher (more forward) will solve this issue. Is there anything else that needs to happen (anti siphon loop valve or loop). I'm trying not to get into reversible pumps or drilling holes in my boat. Thanks for any help

Would putting an inline shutoff valve be out of the question? That way it would only be able to flow when you have the valve open

That's basically the same thing I do with the corks. I just can't adjust the boat when underway if I have it corked/valve closed. I could put silanoid valves in but that's a last result I think. I already have those on the fill side

You make anti siphon loop and the run hose loop up higher than the bag. Wake makers sell these too