You must match your arrow to your bow by that I mean you have to find which spine weight is thebest for the bow you are using regardless of the bow's stated lbs @ it's draw lenght A rule of thumb is 10 to 15# heavier spine weight than the draw weight of the bow. i.e. A 45# bow shold be pushing an arrow of 55 to 60 # spine weight.
There are variables to consider; if using a fast flight string add 5# to spine weight. Remember though each bow is an indiviual what is sauce for the goose may not be sauce for the gander. For instance the bow I shoot (a recurve) uses arrows rated in the 60 to 65# spine weight with a 160gr point and FF string. The bow itself is rated @ 47# at my DL of 30" so ideally my bow should launch an arrow with the SW of 62#
The bowyer recommended a SW of 80 to 85#! with a125gr. point Which would make the arrow way too stiff. A supplier of shafts recommended a SW of 65 to 70# w/ 145 gr. points again way too stiff. I finally settled on the 60 65# SW with the 160gr points and am satisfied as I can now group my arrows within a 7" circle @15 & 20yds on qa fairly consistant basis IF I do my part.