Get take the measurement first, then do the compartments for incoming water from tank, with filter, another compartment for skimmer pump, then refugium, then compartment for fluidised reactor for carbon/phospate/nitrate (whatever), then chiller pump, then no-bubble compartment for return pump(s).
After making drawings on the measurement, head to Kelantan lane, or there's a shop beside GO, to make your sump. 6mm thickness will do.