The top most height of the baffles that are 'fixed' to the bottom of the
sump will dictate the height of the water column in the
sump. With that said, you will want to calculate just how much water will cascade down from the display to the
sump if/when the return pump is shut down. This will let you know if you will have an overflow issue or not. Also, keep in mind that a smallish, drilled hole in the collar of the nozzle end (below the water line) will help break the siphon from the display to the
sump. KEEP IT CLEAN! and you can reduce the gallons that end up in the
sump after the return is shut down.
The baffles that are lifted from the bottom of the
sump (and the distance between said baffles) should be designed with "flow rate" in mind. The tighter the openings (to bottom and to the adjacent baffle), the faster the flow rate through those baffled areas and less likely chance for air bubbles to escape upwards.
Depending on the size and configuration of the
sump plan, you may also want to ensure that you can get into every nook and cranny for cleaning/maintenance purposes.
Dave