Will it make your arrow weaker or stiffer by adding a thicker side plate?
weaker
Makes the arrow act stiffer.
Prairie Drifter is correct. As you build the sideplate out, it will make the arrow act dynamically stiffer. So, if your tuning is showing a weak arrow this would be a remedy. If your arrow is showing stiff, REDUCE the side plate.
Thanks that is what I thought.