Smudge,
Thanks for a very interesting link (Che Sanh Demo). I must say that the C-130 short approach does look a bit "hairy", a real "dirty dive at the runway" in fact, even though you have to take perspective into account, and we don't know how much (if any) headwind was involved.
Having said that, there is no point in making yourself any more of a target for flak than is strictly necessary, and making life harder for the gunners is always a Good Idea. I still think your 20° is a bit OTT, but perhaps 15° is not far off. Poor Hoskins would need to Get the Round Out Just Right, though ! Have we a Hercules driver on frequency ?
The countryside of Viet Nam looks very like N.Burma did in my time.
Danny.