As per topic title...before I set-to can someone give me a clue as to which part(s) of the trank need modifying. I've borrowed a tank from someone who has allegedly modified it to fit a 2011 model but top airbox retaining screws are making imprints in the plastic, the back of the tank won't fit under the front of the air box properly (makes the front of the tank sit high) and the underside looks like it might be pushing down on the rad filler cap when the tank retaining bolt is tightened up. Cheers in advance

You need to be more worried about the front mounting bolt on the middle box getting so hot it melts through the tank...

If its that far out i wouldn't risk it.When you've dented it in enough to get clearance on all the areas mentioned it won't have much more capacity anyway,and it'll be a lot thinner/weaker where you've stretched the plastic to give clearance.I wouldn't chance it/me going up in flames if it leaks out on the pipe,would you?

put washers up front but under the tank? or cut small peice of hose, to spacer it above the radiator up front, and keep the bolt able to go tight, but not squish into radiator?