Paul-

Sorry, but I don't understand your point about choosing your spring length to "center your shock travel". Once you choose your shock brand and length, and decide on your ride height, the shock "center" is going to be wherever it ends up, based on the shock length and the dimensions of your specific car. Seems to me that no matter what length spring you use, the shock rod will end up in the exactly the same place relative to the shock body, unless you change the ride height. The only thing that will change is how high the lower spring mount sits. Or am I missing something? I realize you want to not end up with the shock near either end of its travel (particularly compression), but I don't see how spring length enters into the equation, except as it may limit your ability to set the car at the desired ride height.