Thanks Lou! I saw the term "wing loading" in articles about stalls etc. Now it's time to read about it! And general aircraft aerodynamics.

That "coffin's corner" reminds me of West Caribbean Airways Flight 708.  MD-80 stalled because they flew close to stall speed, with anti-ice on, and sudden updraft pitched nose up, so they exceeded max AoA.

I flew 707 at 36 000 ft max. at about 280 000 lbs at FL360 it looks like it pretty close to stall speed at cruise power setting.

BTW, what would you prefer in situation like this:

You climbing in 707, and you've choose maximum cruise altitude for your take-off weight. Say it 37000 ft. and while at 35-36 000 ft you flew into some turbulence. And since FL370 your max alt for weight, will you decide go lower because of turbulence at max alt can be dangerous because of narrow operational speeds interval?
That question arises in almost every flight i fly in 707.

P.S. I just landed after simulating failures in 707. Worst I had: 2 eng failure + airspeed indicator failure at the same time. Landed safely at flaps 14. The shot i failed today: pitot tube failure. I exceeded Vne and overstressed plane while making turn. Now i'll read, try one more day, and then im sure i'll have a ton of questions  ;)