Tractorboy the point you, and others, are missing is that about half that 1215' you quote from 50' is air distance.....i.e distance travelled BEFORE you get to the threshold.
On short grass strips of the type you are referring to you would typically be touching down around 30-50m in from the actual threshold. Just past the first cone marker. 50' would be easily 200m before that point...over the field before the one you're landing in...and that's why we always SEEM to stop in 'half' the distance reqd by the graphs. Having pulled the figures and buffered them up hill and down dale and decided the strip is 'marginal' we white knuckle our way down and then stop mid field..and wonder why?
The same applies on takeoff...you can, and often do, climb out to that 'magical' 50' past the far end.
In neither case is the 50' point within the confines of the 'flight strip' ...nor does it have to be....in airliners/transport category aircraft we call it Clearway.
God grief as a young fella with 300 hrs I used to operate C185s and Islanders in and out of 385m/3000-5000 elevation and ISA+20...500m in a Cessna 152/172 is a doddle
