Fuel Tank Over The Diff Cage?

[leroybrown911]

Just found this thread as I am soon going to start fabricating a fuel tank and I also want to put it over the diff cage, or even extend the original design up in to this space.

Does anyone have any dimensions or pictures of how much space there is? I do not have my bodywork yet so I have no idea how much room there is or whether I will need to cut any of the fibreglass to make it fit? (I am using a fibreglass rear tub)