I have a 77 Scout II with "stock" windsheild wipers - Trico Triple Action 11". My question, other than if these are really stock, is how do you remove the blades? I can see a notch in the wiper knuckle with what looks like a spring clip inside of it. If I could figure out how to activate this, I think the whole blade would slide off of the wiper arm pin. Does anybody know if you can get these blades off without drilling out the pin?