I prefer to use the real world check. Assuming you are not at the short strip already, make a mental note of your ground roll at your departure field. Most field i fly from have runway centre lines, and someone at the field usually knows the spacing of those lines. With this information you can make an accurate estimate of your ground roll. Then factor in the differences, long/short grass, wet dry and wind etc for your short strip. This method takes out all the unknowns such as how many horses have died since your engine was new! Indeed, many engines NEVER produce the claimed output, the converse of that is occaisionally you will get a "GOOD" engine that seems to out perform all your mates
. Bottom line is know your plane!