The 20 grains of arrow weight under IBO would result in a loss of less than 7 feet per second putting you at 321 at 30# IBO and still within manufactures specifications. On top of that if you read the 2004 owners manual on page 7 you will see it says the tests reported on the birth certificates are done with the vibrablock hush kit and a brass nock installed which result in speed loss of 3-5 fps, which would put you at 324-329 (mid to high advertised speed).