This is it:

As it happened, I just got it working.

Using a trim press is basically like using a cookie cutter, except it cuts leather, rubber, etc. In preparation I made this nice 3" cutter out of pcv.

Unfortunately it wasn't strong enough. When you use the press, you first set the height by pushing down on the cutter in low power mode, you then set this "pressed" height as the stop point. Well, even it low power mode, the the press smashed my cutter :(.

The next time around I set the press height with a PVC ring, THEN I ground an edge onto it.

I took a video of the actual cutting operation so you can see how it works. The press makes it seem so easy.

Link

The edge quality came out great this time. (I cut out the center hole with the press as well). The disk is now smaller than the pipe ID, but that may be a good thing, since this’ll give it room to deform and soften the impact.

Lastly, I glued the bumper to the back plate with the loctite #380. I forgot about the smaller ID and put some extra around the edge. I’ll have to sand that off later. No biggie though.

After applying the glue I clamped the assembly between some boards and left it for 24 hours.

ASSEMBLY. ..After 60 or more hours of machining and designing, I couldn’t wait to test it out.