Stage 1 V8

Hi all, well I have owned my stage 1 for quite a few years now. It's part of the family and my wife is going to bury me in it (not sure when)
I have always had issues with water getting into the petrol tank.
I have tried new gaskets around the sender unit as well as various sealants. All not no avail.
I am pretty sure it's getting at the top of the tank around the sender unit.
Has anybody else had this problem and how did you solve it?

Side tank or rear?

If side, check for rust around the inlet. The sponge holds water and rain can seep into the tank.

Could it be condensation?

it's the rear tank.
i think there is too much for it to be condensation

The only thing I can think of is that it is getting in through the spout somehow. I assume the rubber filler pipe is not leaking.