Best way to run 4 lifeguard Fluidized Bed Filters???

[Hustler]

After playing with them and a measuring tape for a while I figure Ill run the pump out of my sump inline to the bottom of the first, then manifold it across the top and exit the top of the last back into the sump..... Seems to be the least resistance anyways.... If i can make them work with bio pellets, carbon and GFO great as Im still leary of the sand bed as a nitrate factory?
Any ideas or opinions would be greatly appreciated
They are big mothers lol