I have no doubt you are right kube. I just don’t have time for that at the moment.
I just tested the old tank again and now I’m confident it’s leaking under the filler neck where that reinforced piece of metal is.
Edit
Did a 3rd test. Filled it with water, then plugged all the holes and pressurized it ever so slightly with some air. As suspected, water shooting out under the filler neck like a fire hose. Hard to see in photos but now I’m certain this tank is bad. I love aftermarket parts!
IMG_4397.jpg
IMG_4395.jpg