[SJS]

I'm not sure if this will help but here is how I have my tanks set up... I have a 300 display tank, 90 gallon fuge, 35 gallon fuge and 35 gallon sump. The display has 4 overflow/drain lines, 1 line feeds the 90 gallon fuge, 1 feeds the 35 fuge, the other two go directly to the sump. the 90 overflows directly to the sump, the 35 fuge does not have an overflow - I have 2 bulkheads on one end of it, the top of the 35 fuge is higher that the sump, I have 3/4" (or 1") hoses which direct the fuge water to the sump - via gravity. 2 return pumps on the sump directly back to the display.
I have it set up this way so there are minimal pumps, and for the fuges, medium to slow flow.