Brake squeal is caused by vibration. Anything that can be done to stiffen up the brake arms can help. Make sure pad adjustment bolts are tight. This usually cannot be done without leaving the pads askew so the pad adjustment bolt is left short of full tightness. Most V-Brake pads have a complicated assortment of washers and shims to allow pad alignments to eliminate squeal. I've never understood their real purpose. Mostly my various v-brakes (several pairs on various bikes) brakes do not squeal. I upgrade OEM V-Brakes to Shimano V-Brakes in the $2?.00 each price range. Cheap OEM V-Brakes have very weak pad retraction springs and that is more annoying to me than brake squeal. Shimano V-Brakes have no slop at the mounting boss pivot when the bolts are fully tightened. Other v-brakes, even decent ones often have a degree of 'slop' when the pivot bolt is tightened. The OEM v-brakes on our latest tandem (over $1.2k retail) have this problem. Rather than replace them, I am looking for a way to shim the calipers against the main pivot boss to reduce or eliminate the slop. This I feel will address the squeal, and they do squeal. Changing to Kool Stop pads has not fixed it which reinforces my opinion that it is vibration occurring in the pivot arm itself. FWIW.