Actually I am using PAL (UK).
Normally I would not want a long DVD - certainly no more than an hour or so - I am simply curious.
Actually, now I come to think about it, I have used Toast to copy a dual-layer DVD that lasted 4 hours (onto a single layer DVD-R). So presumably there would be no problem with making a 4 hour video in Final Cut and burning it - not that I would actually do such a thing.
With regard to using Custom Settings, I suspect that by fiddling around and tweaking everything to perfection, the improvement would probably be so slight as to be imperceptible.
Still it would be nice to know exactly how to set the parameters for different subjects.