Sam,
The weight of the actual aircraft is irrelevant - any aircraft can be "greased on" with the correct combination of speed (and hence lift) and correct body angle. You are right re. the 767 - it is harder to land, but only because the bogeys are tilted the wrong way. The aircraft has a predilection for "stubbing its toes" because of this, but it is still possible to "squeak her on".
As for the certification process, I understand that the u/c must be able to withstand 1200FPM rate of descent
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400R