A euro trigger is designed to trap the top of the shaft against the top of the trigger housing. An American trigger is designed to hold against the notch in line with the shaft. The forces are 90 degrees apart. So what the half moon notch is doing is transferring the force upwards away from the direction the trigger was designed to hold. The sear of a euro trigger is rounded to fit into that notch- large surface area contact. The sharp angle of Steve's sear will have a high pressure contact there, not ideal by a long shot. $100? Buy a new one mate, trust me, I'm on your side really