Yes, to fasten it to the bumper guard I used weather strip adhesive. Coated both sides, let them dry for 15 minutes and stuck them together

I would love to get some more detailed info on these. What grit sandpaper did you use on the disc sander to shape them? I assume you used an orbital hand sander? Are they painted when you said "coated"? It is just stuck on using weatherstrip adhesive, no other hardware?

Yes, I used weather-strip adhesive, coating both the back of rubber and face of bumper guard.

For "rough" rounding of the edges I used 100 grit on a small bench-top belt sander, then finished using 600 & 1000 grit on a rounded piece of wood, (sanding block).__This was followed by a vigorous buffing/polishing with abrasive polish, then a though solvent cleaning and finally some rubber dressing.

It took some time to make edge radii consistent, (I ruined the first one...).__Probably more effort than the cost of buying one, but there were none available at the time.

Also, I measured the rubber sheet and it was 3/16", not 1/4".