Beananimal Overflow Help

[ReefOcean]

So i need to have the 3 holes drilled for the beananimal overflow in the back of my tank. I have seen many pics and a few youtube videos but i couldnt find any info on the varrying height on the main siphon overflow and the secodary overflow. I assume that the seconday pipe needs tto be completely above the siphon IE if the siphon in is 3 inches below the rin, the secondary needs to be at the very most 2 inches from the rim in order for the siphon to be completely submerged before the seconday takes on the little bit extra flow. I am postibg from phone, so I cant post the video but on youtube, a guy cut the flow down on hhis siphon to raise the water in his overflow box, and it appeared that at the exact point when the the water level completely submeged the siphone elbow pipe, the secondary elbow pipe was 1 quarter submerged suggesting that he didnt have the secondary overflow hole cut completley above the siphon hole. could somebody that knows this paricular overflow help me with the hieght spacings pls.