WUD you are correct about arrow weight and dynamic spine differences. Rob is also making some great points. I can tell from Rob’s posts that he has it figured out what he wants to shoot and then has tweaked that setup to match his bow. It also appears he likes consistency and repeatability in that setup. I would look through his posts and figure out exactly what you are looking for when it comes to total arrow weight, length, tip weight, etc. Then you can order a test kit or a dozen arrows in a spine. You should be able to take multiple spines and tune them to your setup. You will also have a vast difference in total arrow weight and length amongst different spines. I tinker and shoot different spines, total arrow weights, different amounts of foc, different broadheads, etc. I get many setups to shoot well out of the same bow. It’s just a matter of the end result you are looking for.