I have finally gotten my hands on some prototype fulcrum knives for the tremolo! They are made from stainless spring steel, which is hardened to a degree. Too hard, and it becomes brittle and breaks. Also important, the stainless steel it looks nice and comes in a 1 mm thickness so does not require so much machining.
As you can see in the image above, I have not yet finished the base plates since I was eager to test them but I will send some off for finishing later in the week. The stainless steel will work out fine, although it did get some marks after a few hours of abuse. One additional benefit of my design is that the fulcrum will be replaceable. Note also the new logotype!