This is one of the best tools for KSP I've ever used. Thank you so much for putting it together. How difficult would it be to let users specify a dV instead of a payload and payload fraction? I am working backwards toward the number by just lowering the payload fraction and trying the setup, but that takes much longer than just trying something reasonable to start with, but I want to use what you've put together. The design phase is my favorite aspect though, so I enjoy it nonetheless. I would also love to see additional optimization strategies than those you've got--or to have a better understanding of what they mean. Right now, if I calculate for best TWR, does that mean closest to the top of the range I specified? If so, why is that important since any value inside that range must be acceptable? Would it be difficult to add a calculate for isp in a vacuum option? Or average isp over all stages within the model (i.e. all stages described by the app, so ignoring payload stages)? Also, is the center stack size a drop down to avoid calculation time complications? I always wonder whether I ought to jump up to a 3.75 and end up re-running calculations in any case. Again, thank you so much for this tool!