???? So what size are the drain holes in your tank? How many of them are there? How much water can your overflows move? And what size are the holes for the return lines from the pump?
according to this, I could see around 3,000 gph until restricted by my ball valves, so that's crazy turn over for this set up. As long as I match the drains to my pump, I should see 8x turn over an hour at 2,400gph. That's all my pump can put out.http://flexpvc.com/WaterFlowBasedOnPipeSize.shtml
Based on this, you'll probably be alright with a pair of 1.25" drains. Now, how much can your overflows drain? Probably plenty, but you need to check.