It wasn't that high, that steep, or that short. The highest peaks in the area seem to be a bit over 9K, and the LZ was quite a bit lower then that. The slope appears to be about 12% or so. The available runway is 1500' to 2000'? I understand that in this area you just don't pick a site out and land there, like we laregly have the freedom to do, at least in the West. So this was hardly a "first", a one off "pioneer" landing, no more then the guys who visit Idaho in the summer and land Mile Hi, after watching countless videos and reading numerous pilot reports on how to do it.
Like I tried to get across in my second post, I realize there is probably no way I could make this comment without coming off poorly, and sounding like a internet poser, but really that landing is not at all difficult. Scenic, of course, and absolutely cool as heck, but not at all technically difficult to anyone who lands slopes higher, steeper, shorter, and lastly, that have never been landed before. There I go again, that makes me sound like a jerk, but really it's all what you get used to. Flying slopes is all in the eye picture, once you get used to that (I don't know how else to put it, you just learn to handle steep slopes the same way you handle flat landings) I find them actually preferable. You can come in with some power on, and done correctly eliminate any float, just full flying control until you stick it on.
There is also a phenomenon, or there seems to be to me anyway, that I call "up-slope ground effect", but I consistently have my shortest landings anywhere landing on slopes of 12% and up, (not just short, of course the roll out is less), but also slower airspeed wise. Yes, slower then landing on level ground, I swear! Uphill landings are a pilot's friend, once the needed sight picture gets familiar.
I've had two different airstrips in the last 21 years, (and have been a pilot for over 40), both 400' long and about 20' wide. The first at 6150', my current (and last, unless this area gets too built up, like what happened to my first) at 5460'. Both are one way strips, with slopes of 10 to 14% (depending where you measure), I have a 9K+ mountain range immediately behind my place, and land almost nothing BUT slopes, including when on the skis, I really have no choice. I fly a 100 horse RAMS S-7S on 29" Airstreaks (summer) and Datum retracts in the winter. If the OP would have just said "Great vid", or words to that effect, I'd just have said "Indeed"! But it wasn't especially technically difficult, especially as it is an established oft landed area.

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