Originally Posted by Gipsy Queen
Does not some of the constructional weight saved in the pylon system have to be put back to resist torsional factors?
It's more like the other way round.
There is a mass penalty in having a pylon extending well forward of the leading edge, compared to one more directly under the wing, since it's a larger piece of structure and has to take cantilever loads. In other words, such a PYLON is heavier.
But there is a mass SAVING in the basic wing structure, because the fact that a lump of mass (the engine) is so far forward of the wing flexural axis means that the wing can actually be less stiff and still have acceptable flutter margins. So the WING gets lighter.
On balance, it's usually a net structural weight saving to have the engines suspended a decent distance forward, because the weight saving in the WING tends to be greater than the PYLON penalty.