Help with where to silicone overflow

I am ready to silicone my internal overflow to the tank for the bean animal project. Is 1/2" to 5/8" above the black trim okay for the water level, or does it not matter as it's aesthetic purposes only how high the box is set re: the water level?

 

well it depends i am running a 20 gallon long that i made a overflow box for. i didnt have a comb so i bought a straining comb from aquacave when i placed my order from them, my box is 1/2"from the black trim then i took the comb while the tank was running and got my return running at the flow i wanted then i moved the comb up and down found my water depth i wanted and marked it drained tank siliconed it and its been running the way i wanted it to for about 2 weeks now.

if yours has built in teeth i would say you need to fill your tank with fresh water and hold the overflow to the back of the tank and see where your comfortable with your water level at i keep mine about 1/8" above the bottom of the trim. the lowest open part of the comb is about a little more than 3/8" below the bottom of tank trim peice i am running about 250 gallons an hour right now since im goin out of town for a week but when i get back i will crank it back up to the 450gph since its only cycling right now it doesnt bother me to trun it down

just my 2 cents your tank may be to big to run the flow test i did to set my comb height, good luck.