Sump Questions

[LornaS]

Okay I have been thinking of doing this and would like some feedback or advice and I haven't been able to find much on this believe it or not. I want to make a sump/refuge for my 75g. I want to use a rubbermaid storage box about 15 to 20 g and inside the big one I want to put a smaller one that will be the fuge. I would drill or cut holes in the ends of the smaller one for water flow through the fuge. One end would contain the skimmer and inflow the other end would be the pump and heater etc. I would need to have an outside overflow as my tank is not drilled. I would try for a 600 gph overflow with a 1" drain. Is this sufficient? also I would have a return pump rated at 850gph with a ball valve on the return with a 1" return. Am I on the right track here or am I lunched?