You won't lose draining flow rate in your particular set-up. Running ~1200gph on that linear overflow length, then I would worry
Offset the egg crate so that it looks like it's divided in quarters when you look into one of the openings and keep a gap of ~3-5mm b/w the eggcrate. That should do the trick.
I'm not a fan of using netting/screening on eggcrate for preventing overflow "thrill riders". One has to be extra diligent on keeping the screening/netting clean as there is a higher risk of overflowing of the main display should they get clogged.
Move the return outlet to the opposite side of the aquarium WRT the overflow.