A lot of the difficulty that folks have with carbons is none of the Manufacturers label the spine of thier shafts in a consistant manner. You have to research each one of them to determine what is the right shaft for you.
With a 56# and a 60# bow you could shoot the same shaft in both but either your point weight or shaft length would vary between the two. Your 60# would like a little less point weight or a shorter shaft than your 56#.
If you are going to setup for max FOC (front of center) then you are going to have to start with a 300 spine shafts.
Easton = 300
Carbon Express = 250
Gold Tip = 7595
Your draw length also plays a role in the overall out come, so you will need to know what your draw length is for both your bows. It is not uncommon for it to vary between two different bows. A lot of us tend to have a bit shorter draw with a heavier bow over a lighter bow.
Start with your shafts 2″ longer than your draw length (if you can) and get yourself a field point test kit (actually you will need to order 3 test kits to have enough points). Then you will be ready to start your bare shaft tuning. If you would like a procedure for bare shaft tuning PM me with your email address and I’ll send you one. Good luck – Derek