As per my external fuel filter post, I have had the tank repaired.
I "consulted" a welding mate who directed me to a restoration company (they do Rolls Royce renos amongst other fine cars) who have a lot of radiator experience.
We determined the leak was from a cracked spot weld on the hinge to tank union. I meticulously stripped paint around the hinge plate, then blew out all the crap and paint stripper with a steam pressure cleaner.
They then sweated solder all around so that it wicked into all crevices under the offending plate. Another advantage is that solder is lowe temperature than welding and will not buckle the tank nor stuff up the visible paint work.
I showed them the POR-15, which they know of and they advised that this would not be necessary after their fix, so i did not do it
It had a few internal spots of surface rust and they gave me a wet product to spray on to remove the rust with a non metallic kitchen pot scourer - looks like new now.
Cost Australian Dollars 340 - Rolls Royce price? Much cheaper than 3,400 or so for a new tank and it is undoubtably fixed "forever", unlike the original construction!
I'm wondering how well this has held up over a year later?
I'm a bit concerned about soldering since solder is a very light material and it seems to me that it wouldn't hold up very well at all.
I'm starting to have this issue now and am needing to get it fixed ASAP.
FOR SALE - 2002 900SS: Galfer Wave rotors + Carbon front fender + Ducati Performance levers & high mount carbon cans + Cycle Cat clip-ons & triple tree + Evoluzione Slave Cylinder + Motowheels Slipper Clutch + Power Commander w/ custom map + Air box mod & K&N + MBP Touring Wind Screen + Penske front fork rebuild