OK how come when I shoot my bow with the arrows that came with the bow which weigh 560 I get arm slap but when I shoot the new arrows I built which weigh 710 I don't get any arm slap at all. I am shooting 57# at 26.5 draw. I am believing the arrows that came with the bow are to light.
The arrows are light but prefectly in the acceptable weight range for your bow.Arm slap can come from too low a brace height,too tight a nock and a dacron string.
My theory is that the bow shoots more abruptly with the lighter arrow, and you need to hold it more firmly.
If your arrows allow it(still in tune), try a little more brace height. The arm slap may just go away.