Problem with Elephant Poly Bronze Front Bushings, Whipped it! Now swinging freely! Options

[bobhasissues]

Installed the poly bronze front bushings last spring. They were binding. To alleviate some of the binding I bought, from McMaster Carr, spherical washers for the frontside mounts. This helped quite a lot, but there was still a bit of binding. I figured I also needed spherical washers on the backside mounts as well to get these things to rotate without binding. My plan was to replicate the $200 Elephant backside mounts by machining enough material off the top and bottom sides of the backside mounts to accommodate spherical washers. I began this project today.
When I started to take the control arms off the car, every one the base (concave) sides of the washers fell off in pieces. I couldn't believe it. When I assembled this stuff I only gave them a good snug down with a socket wrench, no over tightening.
I do not want to continue this project and modify the backside mounts if the conical washers cannot hold up.
These are the washers I bought for the front mounts, same manufacturer for the backs, just a larger size.

I bought case hardened steel rather than stainless due to the 12 sets x $15 per set price difference.
Has anyone had a similar experience? Any advise to help me get this resolved will be greatly appreciated.