Depends on the width of your sump.
2 inches will be great between baffles themselves and between baffle and bottom. Itll handle much more flow and also allow access for cleaning or taking out things that fall between the baffles.
I always space my baffles with eggcrate placed vertically for seperation. This 1/4" or so allows the water to travel at a high rate of speed reducing algae growth inbetween the baffles as well as reducing micro bubblea from travel from one compartment to the next