What you working on? The build that is.

I'm Struggling to get a even level across all 4 of my pots they are xl oxy pots and a head unit connected via 50mm id diameter pipes. Return pump is 25mm id hose to a newa jet 8000. My nearest pot fills higher then farthest by say 5 inch. I'm thinking either my connected 50mm pipe is too small or my Return pump is overpowered. A 25mm id inline valve is on order too slow the Return feed to the pump to see if I could find the "happy medium". Other then shimming pots up. Any ideas?, anything I'm overlooking. my first design and the physics Is making me scratch my head. Any more information I could give please let me know. Thanks nuggz