Initially I didn’t use teflon there was a very small leak then i used teflon very thin layer. I kept one of the other intake but I have a valve on it so I am able to turn it off any time i need better suction from the skimmer. I would keep only the skimmer if the water level is where it supposed to be all the time but after backwash cleaning losing about an inch water causes some air in the pump because the suction is too powerful and it swallows some air with it. So if I keep the other intake open it has even suction and doesn’t cause any air issue. You might have solve that by installing it about an inch below then only skimmer intake would be fine.
So far have you noticed any issues with putting the screw holes into the seam on the top edge? I definitely wouldn't cut the hole through the seam, but just putting the screw holes there seems like it might work.
The only issue is when i do backwash on the filter and lose some water if only the skimmer intake is active it swallows air because the flow it too much and there is not enough water coming but if i leave the other intake open as well i don’t have any issues it still collecting a lot of debris. If you don’t want to deal with refilling often its better to install right below the seam.
