Help with fuel sender issue. Options

[Marv's3.6six]

Hi guys, I have a problem I have not been able to solve. When a fuel sender is first installed in my tank it will give an initial read of the fuel level in the tank, which is fine… however after that the fuel level never changes, its like the float in the sender tube is stuck at one point.

Here is the twist to my story, I run a PMS 914 “Fuel Safe” fuel cell which is a bladder tank that is filled with FOAM. (see pic 1)

I have spoken to fuel safe tech and they said that from time to time there are fuel cells that will not work with a tube type sender that reads with a float. I have tried 2 fuel senders and both have the same problem.

My assumption is that there is bladder foam material pushing against the bottom of the sender and not allowing the fuel to drain from the senders small weep holes on the bottom. (see pic2)

I have dry tested the sender and gauge. I temporarily wired the sender to operate while I am holding it. With the sender in normal orientation the gauge reads empty. When I flip the sender upside down the gauge reads full. The sender gauge combo operates normally.

Here is my thinking…. what would be the downside for me to drill out the weep holes on the bottom of the sender? If the foam is indeed pushing up against the sender bottom, much larger holes would allow it to drain, right?

Opinions please….

Thank you.