Over the years I have seen discussions and conflicting opinions on whether you can ever be 100% as good as you were pre-surgery. I did 5 CM on Femur (stryde) and based on the way I am progressing I am 100% sure you can become 100% as good as pre-surgery , though the time to reach that stage may vary from person to person. I don't know if that would be the case for 3 inches or more or not, but I think 5 CM is the safest limit and maybe you will gain less (than if you go for the max 7-8 cm) but you are almost guaranteed to be 100% normal. This is my take based on my personal experience.