I have found that if know the speed of a few given weight arrows you can get the program pretty close. You just need to mess with the IBO or AMO speed and efficiency rating until you get the program to give you the same speeds or pretty close for each arrow. It doesn't need to be perfect, within 5 fps or so is plenty accurate.

.15 spine is nothing, I don't worry until it starts to go off the charts. And like Bigcountry said, this thing is not dead no accurate, but it is much closer than any chart or online calculator is. And once you find an arrow that spines right for you bow you can sync or adjust the program to match it. That way in the future it will even more accurate for that particular set up.

I just re installed windows on my computer last week, I hope I can continue using this program, I have not tried to download it again yet to see. I plan on getting a new computer sometime in the future so I don't know if I want to bother with it until then. If I have to purchase a new copy I don't know if I will bother with it or not.

Paul