Not sure if i agree, the maximum stopway is half the takeoff flare distance, so i doubt that its long enough to say that an aircraft enters it as some speed!
Well, if you assumed a 160m stopway and 1/2'g' decel (reasonable for a max effort stop) then assuming you are stop-limited, you'd enter the last 160m of the decel at about 40m/s - something like 75 knots. That's pretty fast.
Granted the constant decel is a bit of an approximation, but it won't be far off. Even if the decel were halved, the entry speed would only drop to about 50 knots or so.