I have Paul Touring Canti with Koolstop Thinline pads. No squeal but it takes a good amount of toe. With the Thinline pads there is a little "kick-out" on the end that's about 1.5mm, and I have about .7mm of toe under the kickout. Also make sure the pad adjustment ball/cup that is closest to the pad is fully seated. I've had some of them not fully seat and leave a gap. Those would occasionally squeal, then then pad would suddenly be loose when the cup finally seated. Now I tap them in place with a drift and a hammer, and I haven't had that issue.
