Ok I know how to calculate what spined shafts one needas depending on their draw length. But I want to know if arrow head wieght can play a part in determining spine. For example will I need stiffer shafts for heavier heads?
Yes point weight will make a diff in shaft spine +/- 25 grains is around the same as +/- 1 inch of shaft length.
Very possible. I haven't had to change going from 125 to 160, but I had to go up 5# for 190. Depends on how close to perfect you are to start with, I think.
I find this site handy nice and simple they way they have explained it. http://brackenburybows.com/Tuning%20Tips.htm