Old,
I shot target archery when I was in high school. My form must be pretty good since I don't wear an arm guard during warmer weather when I'm practicing with short sleeve shirts. The bowstring never slaps my left arm upon arrow release. I think what you're seeing is something different because I'm below the brace height that Norm recommends. I think there are more variables (factors) that we pay no attention to which come into play. My 42# has no string silencers attached to the bowstring. It's whisper quiet too. Do string silencers slightly change the spine of an arrow with regards to point weight? I used to say "no", but now, I've changed my mind.
I'm an enigma. I shoot very light bow poundages coupled with a 32" BOP arrow. I'm also shooting very heavy arrows out of my two bows. My GPPs for both bows is 15.16 and (14.86). Yet, my 2117s and 2114s should be too stiff with the point weights I'm shooting, but both of my bows love these two very heavy arrows because of the brace height I'm using for each bow.
I think people should sometimes think outside of the box and experiment.