Yeah I figured you might have to with the overflow, the water level had to be as low as possible to reduce the first sump chamber, which is still a little too high.
Is the sump level? If the sump is level the water flows against the baffle but if the right side is sagging the water will separate. The eggcrate will work if you want to run a higher water level. You could also hang filter floss on that baffle, the water will have to go down through the floss to get into the second chamber. Don't run the sump too high that you can't turn the pump off.
It would have been better if that second last baffle was taller but that's what you get for working with scraps
