i did something else too. I ralized i had a box of bulkheads that i could not use. Just a reminder, they where threaded, but just from one end, and pipe threads are tapered, so you can only thread into them from one side.
Anyhow, they have very thick gaskets. the new ones have one thick on outside, and a thin one on the inside.
I took the thin one out, and used a thick one from the old ones. It is a little bigger. the nut has a ridage to seal against the gasket on the inside. This other gasket, when tightened goes outside that ridage and seals against the flat of the nut.
Looks like this will fix the prob, so far.
As for this being permanent, I am going to secure some suction cups to the background and leave it in three pieces so i can remove it later if needed.
The only thing i can not remove, is the RUGF plate.
And even then, i think the top of this tank is thick enough, and it is only 18x18, that i could enlarge one of the holes to get it out, without compromising the eurobracing at all. But i would only do that if i really needed to.