Hmmm, to be honest I work the other way around.
I will walk the course a couple of times, work out how to pace/approach each jump and then TELL my horse how many strides to take between fences.
I.e. I may choose between 7 short strides and 5 long strides, depending on if the jump is an oxer or an upright.
So to me, I am not trying to pick strides a certain distance from the jump, I am counting down from a known number if that makes sense.