Help with plumbing my new tank

[PowderBlue]

So I bought Dave's old frag tank and I'm turning it into a shallow reef. It had a 2 inch drain and a 1 inch or 1.5 inch return drilled into a corner overflow. My questions are

1) By the look of the pic could I remove the return bulkhead, and drill the hole to fit another 2 inch bulk head for a herbie style overflow?

 

2)if there is not enough room could I run a 2 inch overflow for the main overflow of the herbie and run the smaller one as the emergency drain?

 

3) My plan is to run a return bulkhead on each top side of the back of the tank where the black tape pieces are, does this seem ok?

 

4) what size return should I run if I do a whole inch drain? 1.5 inch? My pump is plenty strong it's the DCS9000.

 

If none of this sounds correct what should I do?!

 

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[PowderBlue]

Bumpity bump

 

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[pledosophy]

It does not look like there is enough room to widen the hole for a larger secondary drain. But I am not there with a measuring tape to know for sure.

If it were me and I had the moola what I would do would to run the biggest opening (the 2")as the drain which in theory would handle the entire output from that pump if it makes manufactor specs. Then run the second hole as your back up. 

Then I would run the return split through two sea swirls. A single SCWD would be cheaper and still give you some alternation though as well. 

[PowderBlue]

What size do you think for the returns 1 inch or inch and a half?

 

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