I shoot 565 grains out of a 54 lb longbow. I tried adding some 1/4" nylon braid cord to the inside of my carbon express heritage 150's to add some extra weight and to quiet things down since switching to 3 fingers under... and WOW ! The noise was gone and the arrows are stealthy quiet and really penetrate. I also noticed how much better they fly in windy conditions too. I have no idea how much extra weight that I've added to the arrow, and really don't care since this setup will be used only for hunting in Missouri this fall at distances of less than 20 yards.

525 gr from a 46# bow ........ 11.4 seems to be the right set up for me.

550 gr from a 50# bow.