@EstolidaMelopea:
You don't actually HAVE to remove the power jack to install the crash knob. I think the better way to do it is to cut the lead coming from the jack then installing the adjustment on both sides of the cut. The crash will work best when the keyboard is battery powered. It probably won't work when you use a power adapter. 

I've never worked on the SA-40 but the SA-X bends will probably work.