trembow, that's good link to some useful information...
You can use the following to work backwards off listed IBO specs, this will put you pretty darn close to chrono:
IBO Specs - 30" draw/70lb draw weight and a 350gr arrow.
For every inch of draw length you go down you will lose 10 FPS
For every 5# draw weight you go down you will lose 10 FPS
For every 3 grains of weight your arrow is over IBO ( 5 grains per pound) you will lose 1 FPS
For every 3 grains of weight you add to your string you will lose 1 FPS.
I wonder how many of the masses who shoot a 29" draw length (which I feel is by far more of the "norm" than anything out there...) and pull around 65 lbs. realize they just lost
20 fps off the listed IBO specs just right there!! [
]Throw in a hunting-weight arrow, add a brass nock, tie in a peep and add a couple string leeches, and it's no wonder so many people are discouraged the first time they shoot their bow through a chrono!!