For an aircraft, balance (centre of gravity) is critical. Model turbines are quite inefficient so
a relatively large amount of fuel has to be carried. Through necessity the fuel must be carried close to
the centre of gravity so the balance is not upset too much as fuel is used. If you disregard the balance
issue the position of the fuel tank can be some distance from the engine as model turbines use a pump
to supply fuel.

There's quite a few methods to shield the model from the heat. These include foil tape, woven ceramic
blanket, ceramic paint. Models with engines mounted internally use a stainless steel pipe to direct the
exhaust away from the model.

Hope that's the info you need. - John.