Well generally if I'm dealing with a BWB fuselage such as an Su-27 or F-16, I'd probably map it top/bottom splitting it along the leading edge of the wing. The thing is, the less seams you have the better, since the engine has to deal with all these UV points in the same manner as vertices which means that if you have lots and lots of seams on a model, it will run worse compared to one that is stretched a bit but has only one or two seams. Again, it really helps if you plan out your texture layout before you even start to model, since you can then make things considerably easier for yourself by strategically placing edges along where important panel lines go on the plane.