There is no real right or wrong. basically, get your fuel as close to the cg as possible. But slightly forward is best. and the rest is where it will fit.
Then, you will find that the batteries will need to be in the nose.
The issue with a jet is that engines can have significant weight differences, and in turn, will change how much led you will need to make it fly.
I have a Shock jet with a JC Falcon, and I only needed a few oz of led, with some large batteries up front. (two 2200mah LiFe, and a 5000mah LiPo)