IMO .....Your trays are pack solid there, also those sponges would be a big issue with flow, think I would just stay with just Rena's Bio stars or ceramic rings.
like the other poster stated you must have The Rens's course filters on the very bottom tray & not the top tray....
on my Xp 2 I have the 2 course Rena filters on the bottom tray with 12 Rena Bio stars on top of the course filters, then on my top tray I have a small bag of JBL ceramic rings and then the Polishing filter on top.
I get great flow. I also clean the Rena about every 3 weeks as I can not go any longer than that.....it gets pretty dirty.