Success with removing large top dent in fuel tank with air bladder

I picked up this 82 KZ1000 LTD tank for $75 shipped but it had a big ol dent that needed to be pulled out....about an inch.
 

Here's the setup. Cheap, disposable, plastic 16oz bottle with an air hose attached to the lid. These are Pure Life brand which are very thin and can be manipulated easily. I fold these length wise and push them in through the gas cap. Inflating the bottle pushes against the tank tunnel and pops the dent out. I used a ratchet strap around the tank to keep it in shape as pushing against the tunnel will want to spread the tank slightly. Finally, I used a propane torch to warm up the area which will let the metal to move a bit easier.
 

Got the fill cap pushed out with the first bottle.
 

Couple more bottles to get the rest most of the way out. Everything is within 1/8in of where it should be. Couldnt get the rest because the bottle was too small in diameter for the increasing gap between the tunnel and top of the tank.  These do explode by the way... might take a few attempts. 


Fits perfect on the bike still. I got it within 1/16 with some dolly and hammer shenanigans through the filler and level sensor holes. Will get blasted and bondo etc still.
 

What a great technique, top work