Relax, hehe. No definite setup for sump but those you saw at lfs, did u see the full setup and also how long it took to mature and stablise . . Also, the stocks are meant for turnover and setup may not be suit serious reefers. Have open concept is good for flexibility but u have to consider bubbles, big particles that might harm yr skimmer, etc. Maybe u just do 2 to 3 partition to separate filter, skimmer and return part.