I still use the kick back bolts, I believe if memory is right I have only broken two of those bolts so it hasn't been an issue with me. I did use a longer bolt and a stack of washers on them to keep the blade from going back and hanging up on them. I am thankful that the bolts that hold the blades on has never broke on my machine, that is a scary thought.I quit using the back stop bolt. Just another thing to break. So what's breaking is the bolt holding the blade on.
I notice that the new spacers are smaller in diameter than the old ones. Today I had a blade hang up (clear with a few hammer taps) and noticed that the washer was bent. This is the one I put on yesterday. The extra gap between the spacer and the blade puts more stress on the washer.I will start using grade 8 bolts and washers now. Maybe a double washer.