Back in the workshop, but I only had couple of hours for some serious engineering and designing.
Decided not to cut the tank into three pieces, instead I cut the areas off from lower side to make the
tank fit. Probably will cut the whole lower side off and weld VFR tank's lower side to it.
Also cut the VFR tank into half - lot of sludge inside
Lower side of it, which I'm thinking to use
VFR gas cap fits the GS tank opening but to lock it some mods are needed
So the result should be something like below
Area where the additional tank volume will be added