[nightdriver]

"...some how make it lighter with composite panels ( unless it already is ) and some how ( that is ? if it is safe and feasible to so ) to put fuel tanks in that shroud under the fuselage ?"

I no longer work at the "Lazy 'B'," but, believe it or not, composits do not always result in lower weight. It all depends on what the structural considerations dictate.

As to adding volume for fuel - the plane has a "wet wing," which means that there are no tanks in the plane, per se. The first 747 model had a dry weight of some 360,000 pounds and could carry some 53,000 gallons of fuel, if need be.

That was utilizing a center main tank which was in the wing section right under the fuselage. The old bird had plenty of available volume for fuel, the limiting factor was weight. If it was completely full of fuel, there wasn't much carrying capacity left over for payload.

[Prophet in the wilderness]

Doesn't the 747-400ER have a extra fuel tank in the vertical tail of the plane that was a option for the airline to take out at it's own will ?
Yes, I know most of the airplane's fuel capacity is in the wings ( sealed areas in the wing ).
Then again, it was just a idea, thinking of ways to always improve on the 747.
I guess the added fuel tanks would add weight to the plane in it's initial stage of flight, then, could not reach optimal flight level and it would not be economical until that fuel is burned off.
My mind is always running and thinking of innovative ways ( even if I don't hold a engineer degree, and I am not a engineer at Boeing ) to improve.