Herbie overflow dual overflow

[Locke]

I'm converting my regular durso dual overflow to the herbie method and have a couple of questions.

1. Should I run 2 emergency drains and 2 siphons and then run the return lines over the top of the tank?

2. Should I use the 1" bulkheads as the siphons and the 3/4" bulkheads as the emergency drain or the other way around?

[spit.fire]

I usually run the 3/4 as siphons and I go 2 siphons and 2 emergencies when I convert tanks. If its a running system I go over the back for return if not running I drill 2 holes at the top of the back for returns

[George]

I'm converting my regular durso dual overflow to the herbie method and have a couple of questions.

1. Should I run 2 emergency drains and 2 siphons and then run the return lines over the top of the tank?

2. Should I use the 1" bulkheads as the siphons and the 3/4" bulkheads as the emergency drain or the other way around?

Running return over the top is fine. I am running mine this way because I didn't want to drill an extra hole for the return. More holes=more chances of leaking.
The emergency drain should be as big as, or bigger than, the main drain. The reason is that you want the emergency drain to handle all the flow of the main drain in the case of the main drain getting blocked.