What height/model oscillating tower fan did you go with for a 4x4ft grow? And if you have one, did it eliminate the need for those smaller clip on fans? i.e. is one tower fan all you need?
Depending on how you have things set up you may not need any fan. I have passive intake using three bottom vents. The filter is at the top of the tent so the air is pulled from the bottom to the top of the tent 24/7. I don't have any fans in the tent. I think a large oscillating fan in a 4x4 would be overkill. Air exchange is the main thing you want and you can get that and decent airflow in a small 4x4 tent by just placing your exhaust intake at the top of the tent.
I know everyone thinks you need additional fans in the tent. You don't. A small 6" clip-on fan is more than adequate to create a breeze in a 4x4 tent. I don't even use those. I've stood in the tent and can feel the air moving from the bottom to the top where the exhaust intake is located. The main goal is to replace the air in the tent not just move it around.
I don't have one in my tent anymore, but I just use a couple ratchet hangers wrapped around the fan, or a couple straps like the ones that come with carbon filters.
Sorry about the pictures. The fan is in a tight spot and it's lights out atm.