If it helps, when designing a course I take into account the kill size, the distance and the shooter's position (standing, kneeling, freestyle) as measurable parameters. Such things as wind exposure are daily condition variable and more difficult to put numbers to.
I work on the basis that rangefinding the long targets is important, and to a slightly lesser extent so it is with the very short ones, as it's easy to miss a 9 yard mini kill. If you mis-range a 25 to 30 yarder then it often doesn't matter. So I take the actual distance then apply a factor to create an index of difficulty for that distance. A little bit of arithmetic: call the distance D. The factor I use is D x (1+(abs(D-30)^2)/1000). This gives a factor of 1 for 30 yards, and increasingly above 1 as the range differs from 30.
Then I apply a factor for the kill zone diameter. If you want to know that number you'll have to pay me a lot of money first.
Finally a factor for the shooting position, 1 for freestyle, 1.3 for kneeling, and (another secret!) for standing.
Multiplying all the factors together gives me an overall "difficulty" for that target, then I can decide how to arrange them, for example make the course of uniform difficulty from start to finish (which is useful if you need to split it into 2 for a showdown), make one lane a real stinker, or weight it so that the first few easy lanes suck them in, and the last few are the killers.